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.c

@@ -73,22 +73,17 @@
 // Todo(stefan991): remove this macro
 #define INVALID_DEVICE_ID UINT64_MAX
 
-static char_u   *buflist_match(regprog_T *prog, buf_T *buf);
-# define HAVE_BUFLIST_MATCH
-static char_u   *fname_match(regprog_T *prog, char_u *name);
-static void buflist_setfpos(buf_T *buf, win_T *win, linenr_T lnum,
-                            colnr_T col, int copy_options);
-static wininfo_T *find_wininfo(buf_T *buf, int skip_diff_buffer);
-static buf_T *buflist_findname_file_info(char_u *ffname, FileInfo *file_info);
-static int otherfile_buf(buf_T *buf, char_u *ffname, FileInfo *file_info);
-static int buf_same_ino(buf_T *buf, FileInfo *file_info);
-static int ti_change(char_u *str, char_u **last);
-static int append_arg_number(win_T *wp, char_u *buf, int buflen, int add_file);
-static void free_buffer(buf_T *);
-static void free_buffer_stuff(buf_T *buf, int free_options);
-static void clear_wininfo(buf_T *buf);
+#define HAVE_BUFLIST_MATCH
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "buffer.c.generated.h"
+#endif
+
+#ifdef UNIX
+# define dev_T dev_t
+#else
+# define dev_T unsigned
+#endif
 
-static void insert_sign(buf_T *buf, signlist_T *prev, signlist_T *next, int id, linenr_T lnum, int typenr);
 
 static char *msg_loclist = N_("[Location List]");
 static char *msg_qflist = N_("[Quickfix List]");
@@ -791,7 +786,6 @@ do_bufdel (
 }
 
 
-static int empty_curbuf(int close_others, int forceit, int action);
 
 /*
  * Make the current buffer empty.
@@ -2014,7 +2008,6 @@ static void buflist_setfpos(buf_T *buf, win_T *win, linenr_T lnum, colnr_T col,
   return;
 }
 
-static int wininfo_other_tab_diff(wininfo_T *wip);
 
 /*
  * Return TRUE when "wip" has 'diff' set and the diff is only for another tab
@@ -4016,7 +4009,6 @@ void ex_buffer_all(exarg_T *eap)
 }
 
 
-static int chk_modeline(linenr_T, int);
 
 /*
  * do_modelines() - process mode lines for the current file