Removes 'proto' dir

See #137 for the issue.

Every header in the proto directory was:

* Given include guards in the form

    #ifndef NEOVIM_FILENAME_H
    #define NEOVIM_FILENAME_H
        ...
    #endif /* NEOVIM_FILENAM_H */

* Renamed from *.pro -> *.h
* Moved from src/proto/ to src/

This would have caused conficts with some existing headers in src/;
rather than merge these conflicts now (which is a whole other can of
worms involving multiple and conditional inclusion), any header in src/
with a conflicting name was renamed from *.h -> *_defs.h (which may or
may not actually describe its purpose, the change is purely a
namespacing issue).

Once all of these changes were made a script was developed to determine
what #includes needed to be added to each source file to describe its
dependencies and allow it to compile; because the script is so short
and I'll just list it here:

    #! /bin/bash

    cd $(dirname $0)

    # Scrapes `make` output for provided error messages and outputs #includes
    # needed to resolve them.
    #   $1 : part of the clang error message between filename and identifier
    list_missing_includes() {
        for file_missing_pair in $(CC=clang make 2>&1 >/dev/null | sed -n "s/\/\(.*\.[hc]\).*$1.*'\(.*\)'.*/\1:\2/p"); do
            fields=(${file_missing_pair//:/ })
            source_file=${fields[0]}
            missing_func=${fields[1]}
            # Try to find the declaration of the missing function.
            echo $(basename $source_file) \
                \#include \"$(grep -r "\b$missing_func __ARGS" | sed -n "s/.*\/\(.*\)\:.*/\1/p")\"
        # Remove duplicates
        done | sort | uniq
    }

    echo "Finding missing function prototypes..."
    list_missing_includes "implicit declaration of function"
    echo "Finding missing identifier declarations..."
    list_missing_includes "use of undeclared identifier"

Each list of required headers was added by hand in the following format:

    #include "vim.h"
    #include "*_defs.h"
    #include "filename.h"
    /* All other includes in same module here, in alphabetical order. */
    /* All includes from other modules (e.g. "os/*.h") here in alphabetical
     * order. */

src/buffer.h

@@ -0,0 +1,84 @@
+#ifndef NEOVIM_BUFFER_H
+#define NEOVIM_BUFFER_H
+/* buffer.c */
+int open_buffer __ARGS((int read_stdin, exarg_T *eap, int flags));
+int buf_valid __ARGS((buf_T *buf));
+void close_buffer __ARGS((win_T *win, buf_T *buf, int action, int abort_if_last));
+void buf_clear_file __ARGS((buf_T *buf));
+void buf_freeall __ARGS((buf_T *buf, int flags));
+void goto_buffer __ARGS((exarg_T *eap, int start, int dir, int count));
+void handle_swap_exists __ARGS((buf_T *old_curbuf));
+char_u *do_bufdel __ARGS((int command, char_u *arg, int addr_count,
+                          int start_bnr, int end_bnr,
+                          int forceit));
+int do_buffer __ARGS((int action, int start, int dir, int count, int forceit));
+void set_curbuf __ARGS((buf_T *buf, int action));
+void enter_buffer __ARGS((buf_T *buf));
+void do_autochdir __ARGS((void));
+buf_T *buflist_new __ARGS((char_u *ffname, char_u *sfname, linenr_T lnum,
+                           int flags));
+void free_buf_options __ARGS((buf_T *buf, int free_p_ff));
+int buflist_getfile __ARGS((int n, linenr_T lnum, int options, int forceit));
+void buflist_getfpos __ARGS((void));
+buf_T *buflist_findname_exp __ARGS((char_u *fname));
+buf_T *buflist_findname __ARGS((char_u *ffname));
+int buflist_findpat __ARGS((char_u *pattern, char_u *pattern_end, int unlisted,
+                            int diffmode,
+                            int curtab_only));
+int ExpandBufnames __ARGS((char_u *pat, int *num_file, char_u ***file,
+                           int options));
+buf_T *buflist_findnr __ARGS((int nr));
+char_u *buflist_nr2name __ARGS((int n, int fullname, int helptail));
+void get_winopts __ARGS((buf_T *buf));
+pos_T *buflist_findfpos __ARGS((buf_T *buf));
+linenr_T buflist_findlnum __ARGS((buf_T *buf));
+void buflist_list __ARGS((exarg_T *eap));
+int buflist_name_nr __ARGS((int fnum, char_u **fname, linenr_T *lnum));
+int setfname __ARGS((buf_T *buf, char_u *ffname, char_u *sfname, int message));
+void buf_set_name __ARGS((int fnum, char_u *name));
+void buf_name_changed __ARGS((buf_T *buf));
+buf_T *setaltfname __ARGS((char_u *ffname, char_u *sfname, linenr_T lnum));
+char_u *getaltfname __ARGS((int errmsg));
+int buflist_add __ARGS((char_u *fname, int flags));
+void buflist_slash_adjust __ARGS((void));
+void buflist_altfpos __ARGS((win_T *win));
+int otherfile __ARGS((char_u *ffname));
+void buf_setino __ARGS((buf_T *buf));
+void fileinfo __ARGS((int fullname, int shorthelp, int dont_truncate));
+void col_print __ARGS((char_u *buf, size_t buflen, int col, int vcol));
+void maketitle __ARGS((void));
+void resettitle __ARGS((void));
+void free_titles __ARGS((void));
+int build_stl_str_hl __ARGS((win_T *wp, char_u *out, size_t outlen, char_u *fmt,
+                             int use_sandbox, int fillchar, int maxwidth,
+                             struct stl_hlrec *hltab,
+                             struct stl_hlrec *tabtab));
+void get_rel_pos __ARGS((win_T *wp, char_u *buf, int buflen));
+char_u *fix_fname __ARGS((char_u *fname));
+void fname_expand __ARGS((buf_T *buf, char_u **ffname, char_u **sfname));
+char_u *alist_name __ARGS((aentry_T *aep));
+void do_arg_all __ARGS((int count, int forceit, int keep_tabs));
+void ex_buffer_all __ARGS((exarg_T *eap));
+void do_modelines __ARGS((int flags));
+int read_viminfo_bufferlist __ARGS((vir_T *virp, int writing));
+void write_viminfo_bufferlist __ARGS((FILE *fp));
+char_u *buf_spname __ARGS((buf_T *buf));
+int find_win_for_buf __ARGS((buf_T *buf, win_T **wp, tabpage_T **tp));
+void buf_addsign __ARGS((buf_T *buf, int id, linenr_T lnum, int typenr));
+linenr_T buf_change_sign_type __ARGS((buf_T *buf, int markId, int typenr));
+int buf_getsigntype __ARGS((buf_T *buf, linenr_T lnum, int type));
+linenr_T buf_delsign __ARGS((buf_T *buf, int id));
+int buf_findsign __ARGS((buf_T *buf, int id));
+int buf_findsign_id __ARGS((buf_T *buf, linenr_T lnum));
+int buf_findsigntype_id __ARGS((buf_T *buf, linenr_T lnum, int typenr));
+int buf_signcount __ARGS((buf_T *buf, linenr_T lnum));
+void buf_delete_signs __ARGS((buf_T *buf));
+void buf_delete_all_signs __ARGS((void));
+void sign_list_placed __ARGS((buf_T *rbuf));
+void sign_mark_adjust __ARGS((linenr_T line1, linenr_T line2, long amount,
+                              long amount_after));
+void set_buflisted __ARGS((int on));
+int buf_contents_changed __ARGS((buf_T *buf));
+void wipe_buffer __ARGS((buf_T *buf, int aucmd));
+/* vim: set ft=c : */
+#endif /* NEOVIM_BUFFER_H */