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/fold.h

@@ -13,53 +13,8 @@ typedef struct foldinfo {
                                    line */
 } foldinfo_T;
 
-void copyFoldingState(win_T *wp_from, win_T *wp_to);
-int hasAnyFolding(win_T *win);
-int hasFolding(linenr_T lnum, linenr_T *firstp, linenr_T *lastp);
-int hasFoldingWin(win_T *win, linenr_T lnum, linenr_T *firstp,
-                  linenr_T *lastp, int cache,
-                  foldinfo_T *infop);
-int foldLevel(linenr_T lnum);
-int lineFolded(win_T *win, linenr_T lnum);
-long foldedCount(win_T *win, linenr_T lnum, foldinfo_T *infop);
-int foldmethodIsManual(win_T *wp);
-int foldmethodIsIndent(win_T *wp);
-int foldmethodIsExpr(win_T *wp);
-int foldmethodIsMarker(win_T *wp);
-int foldmethodIsSyntax(win_T *wp);
-int foldmethodIsDiff(win_T *wp);
-void closeFold(linenr_T lnum, long count);
-void closeFoldRecurse(linenr_T lnum);
-void opFoldRange(linenr_T first, linenr_T last, int opening,
-                 int recurse,
-                 int had_visual);
-void openFold(linenr_T lnum, long count);
-void openFoldRecurse(linenr_T lnum);
-void foldOpenCursor(void);
-void newFoldLevel(void);
-void foldCheckClose(void);
-int foldManualAllowed(int create);
-void foldCreate(linenr_T start, linenr_T end);
-void deleteFold(linenr_T start, linenr_T end, int recursive,
-                int had_visual);
-void clearFolding(win_T *win);
-void foldUpdate(win_T *wp, linenr_T top, linenr_T bot);
-void foldUpdateAll(win_T *win);
-int foldMoveTo(int updown, int dir, long count);
-void foldInitWin(win_T *new_win);
-int find_wl_entry(win_T *win, linenr_T lnum);
-void foldAdjustVisual(void);
-void foldAdjustCursor(void);
-void cloneFoldGrowArray(garray_T *from, garray_T *to);
-void deleteFoldRecurse(garray_T *gap);
-void foldMarkAdjust(win_T *wp, linenr_T line1, linenr_T line2,
-                    long amount,
-                    long amount_after);
-int getDeepestNesting(void);
-char_u *get_foldtext(win_T *wp, linenr_T lnum, linenr_T lnume,
-                     foldinfo_T *foldinfo,
-                     char_u *buf);
-void foldtext_cleanup(char_u *str);
-int put_folds(FILE *fd, win_T *wp);
 
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "fold.h.generated.h"
+#endif
 #endif /* NVIM_FOLD_H */