Add automatic generation of headers

- The 'stripdecls.py' script replaces declarations in all headers by includes to
  generated headers.
  `ag '#\s*if(?!ndef NEOVIM_).*((?!#\s*endif).*\n)*#ifdef INCLUDE_GENERATED'`
  was used for this.
- Add and integrate gendeclarations.lua into the build system to generate the
  required includes.
- Add -Wno-unused-function
- Made a bunch of old-style definitions ANSI

This adds a requirement: all type and structure definitions must be present
before INCLUDE_GENERATED_DECLARATIONS-protected include.

Warning: mch_expandpath (path.h.generated.h) was moved manually. So far it is
the only exception.

src/nvim/buffer.h

@@ -1,81 +1,7 @@
 #ifndef NVIM_BUFFER_H
 #define NVIM_BUFFER_H
-/* buffer.c */
-int open_buffer(int read_stdin, exarg_T *eap, int flags);
-int buf_valid(buf_T *buf);
-void close_buffer(win_T *win, buf_T *buf, int action, int abort_if_last);
-void buf_clear_file(buf_T *buf);
-void buf_freeall(buf_T *buf, int flags);
-void goto_buffer(exarg_T *eap, int start, int dir, int count);
-void handle_swap_exists(buf_T *old_curbuf);
-char_u *do_bufdel(int command, char_u *arg, int addr_count,
-                  int start_bnr, int end_bnr,
-                  int forceit);
-int do_buffer(int action, int start, int dir, int count, int forceit);
-void set_curbuf(buf_T *buf, int action);
-void enter_buffer(buf_T *buf);
-void do_autochdir(void);
-buf_T *buflist_new(char_u *ffname, char_u *sfname, linenr_T lnum,
-                   int flags);
-void free_buf_options(buf_T *buf, int free_p_ff);
-int buflist_getfile(int n, linenr_T lnum, int options, int forceit);
-void buflist_getfpos(void);
-buf_T *buflist_findname_exp(char_u *fname);
-buf_T *buflist_findname(char_u *ffname);
-int buflist_findpat(char_u *pattern, char_u *pattern_end, int unlisted,
-                    int diffmode,
-                    int curtab_only);
-int ExpandBufnames(char_u *pat, int *num_file, char_u ***file,
-                   int options);
-buf_T *buflist_findnr(int nr);
-char_u *buflist_nr2name(int n, int fullname, int helptail);
-void get_winopts(buf_T *buf);
-pos_T *buflist_findfpos(buf_T *buf);
-linenr_T buflist_findlnum(buf_T *buf);
-void buflist_list(exarg_T *eap);
-int buflist_name_nr(int fnum, char_u **fname, linenr_T *lnum);
-int setfname(buf_T *buf, char_u *ffname, char_u *sfname, int message);
-void buf_set_name(int fnum, char_u *name);
-void buf_name_changed(buf_T *buf);
-buf_T *setaltfname(char_u *ffname, char_u *sfname, linenr_T lnum);
-char_u *getaltfname(int errmsg);
-int buflist_add(char_u *fname, int flags);
-void buflist_slash_adjust(void);
-void buflist_altfpos(win_T *win);
-int otherfile(char_u *ffname);
-void buf_setino(buf_T *buf);
-void fileinfo(int fullname, int shorthelp, int dont_truncate);
-void col_print(char_u *buf, size_t buflen, int col, int vcol);
-void maketitle(void);
-void resettitle(void);
-void free_titles(void);
-int build_stl_str_hl(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(win_T *wp, char_u *buf, int buflen);
-void fname_expand(buf_T *buf, char_u **ffname, char_u **sfname);
-char_u *alist_name(aentry_T *aep);
-void do_arg_all(int count, int forceit, int keep_tabs);
-void ex_buffer_all(exarg_T *eap);
-void do_modelines(int flags);
-int read_viminfo_bufferlist(vir_T *virp, int writing);
-void write_viminfo_bufferlist(FILE *fp);
-char_u *buf_spname(buf_T *buf);
-int find_win_for_buf(buf_T *buf, win_T **wp, tabpage_T **tp);
-void buf_addsign(buf_T *buf, int id, linenr_T lnum, int typenr);
-linenr_T buf_change_sign_type(buf_T *buf, int markId, int typenr);
-int buf_getsigntype(buf_T *buf, linenr_T lnum, int type);
-linenr_T buf_delsign(buf_T *buf, int id);
-int buf_findsign(buf_T *buf, int id);
-int buf_findsign_id(buf_T *buf, linenr_T lnum);
-void buf_delete_signs(buf_T *buf);
-void buf_delete_all_signs(void);
-void sign_list_placed(buf_T *rbuf);
-void sign_mark_adjust(linenr_T line1, linenr_T line2, long amount,
-                      long amount_after);
-void set_buflisted(int on);
-int buf_contents_changed(buf_T *buf);
-void wipe_buffer(buf_T *buf, int aucmd);
 
-#endif /* NVIM_BUFFER_H */
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "buffer.h.generated.h"
+#endif
+#endif  // NVIM_BUFFER_H