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/ex_getln.h

@@ -0,0 +1,69 @@
+#ifndef NEOVIM_EX_GETLN_H
+#define NEOVIM_EX_GETLN_H
+/* ex_getln.c */
+char_u *getcmdline __ARGS((int firstc, long count, int indent));
+char_u *getcmdline_prompt __ARGS((int firstc, char_u *prompt, int attr,
+                                  int xp_context,
+                                  char_u *xp_arg));
+int text_locked __ARGS((void));
+void text_locked_msg __ARGS((void));
+int curbuf_locked __ARGS((void));
+int allbuf_locked __ARGS((void));
+char_u *getexline __ARGS((int c, void *cookie, int indent));
+char_u *getexmodeline __ARGS((int promptc, void *cookie, int indent));
+int cmdline_overstrike __ARGS((void));
+int cmdline_at_end __ARGS((void));
+colnr_T cmdline_getvcol_cursor __ARGS((void));
+void free_cmdline_buf __ARGS((void));
+void putcmdline __ARGS((int c, int shift));
+void unputcmdline __ARGS((void));
+int put_on_cmdline __ARGS((char_u *str, int len, int redraw));
+char_u *save_cmdline_alloc __ARGS((void));
+void restore_cmdline_alloc __ARGS((char_u *p));
+void cmdline_paste_str __ARGS((char_u *s, int literally));
+void redrawcmdline __ARGS((void));
+void redrawcmd __ARGS((void));
+void compute_cmdrow __ARGS((void));
+void gotocmdline __ARGS((int clr));
+char_u *ExpandOne __ARGS((expand_T *xp, char_u *str, char_u *orig, int options,
+                          int mode));
+void ExpandInit __ARGS((expand_T *xp));
+void ExpandCleanup __ARGS((expand_T *xp));
+void ExpandEscape __ARGS((expand_T *xp, char_u *str, int numfiles, char_u *
+                          *files,
+                          int options));
+char_u *vim_strsave_fnameescape __ARGS((char_u *fname, int shell));
+void tilde_replace __ARGS((char_u *orig_pat, int num_files, char_u **files));
+char_u *sm_gettail __ARGS((char_u *s));
+char_u *addstar __ARGS((char_u *fname, int len, int context));
+void set_cmd_context __ARGS((expand_T *xp, char_u *str, int len, int col));
+int expand_cmdline __ARGS((expand_T *xp, char_u *str, int col, int *matchcount,
+                           char_u ***matches));
+int ExpandGeneric __ARGS((expand_T *xp, regmatch_T *regmatch, int *num_file,
+                          char_u ***file, char_u *((*func)(expand_T *, int)),
+                          int escaped));
+char_u *globpath __ARGS((char_u *path, char_u *file, int expand_options));
+void init_history __ARGS((void));
+int get_histtype __ARGS((char_u *name));
+void add_to_history __ARGS((int histype, char_u *new_entry, int in_map, int sep));
+int get_history_idx __ARGS((int histype));
+char_u *get_cmdline_str __ARGS((void));
+int get_cmdline_pos __ARGS((void));
+int set_cmdline_pos __ARGS((int pos));
+int get_cmdline_type __ARGS((void));
+char_u *get_history_entry __ARGS((int histype, int idx));
+int clr_history __ARGS((int histype));
+int del_history_entry __ARGS((int histype, char_u *str));
+int del_history_idx __ARGS((int histype, int idx));
+void remove_key_from_history __ARGS((void));
+int get_list_range __ARGS((char_u **str, int *num1, int *num2));
+void ex_history __ARGS((exarg_T *eap));
+void prepare_viminfo_history __ARGS((int asklen, int writing));
+int read_viminfo_history __ARGS((vir_T *virp, int writing));
+void finish_viminfo_history __ARGS((void));
+void write_viminfo_history __ARGS((FILE *fp, int merge));
+void cmd_pchar __ARGS((int c, int offset));
+int cmd_gchar __ARGS((int offset));
+char_u *script_get __ARGS((exarg_T *eap, char_u *cmd));
+/* vim: set ft=c : */
+#endif /* NEOVIM_EX_GETLN_H */