More xmalloc and related cleanup.

More xmalloc and related cleanup.

* alloc.c, bidi.c, buffer.c, buffer.h, bytecode.c, callint.c:
* callproc.c, charset.c, coding.c, composite.c, data.c, dispnew.c:
* doc.c, editfns.c, emacs.c, eval.c, fileio.c, filelock.c, fns.c:
* font.c, fontset.c, frame.c, fringe.c, ftfont.c, ftxfont.c, gmalloc.c:
* gtkutil.c, image.c, keyboard.c, keymap.c, lread.c, macros.c, menu.c:
* nsfns.m, nsfont.m, nsmenu.m, nsterm.m, print.c, process.c, ralloc.c:
* regex.c, region-cache.c, scroll.c, search.c, sound.c, syntax.c:
* sysdep.c, term.c, termcap.c, unexmacosx.c, window.c, xdisp.c:
* xfaces.c, xfns.c, xftfont.c, xgselect.c, xmenu.c, xrdb.c, xselect.c:
* xterm.c:
Omit needless casts involving void * pointers and allocation.
Prefer "P = xmalloc (sizeof *P)" to "P = xmalloc (sizeof (TYPE_OF_P))",
as the former is more robust if P's type is changed.
Prefer xzalloc to xmalloc + memset 0.
Simplify malloc-or-realloc to realloc.
Don't worry about xmalloc returning a null pointer.
Prefer xstrdup to xmalloc + strcpy.
* editfns.c (Fmessage_box): Grow message_text by at least 80 when
growing it.
* keyboard.c (apply_modifiers_uncached): Prefer local array to
alloca of a constant.