Shrink the git binary a bit by avoiding unnecessary inline functions

Shrink the git binary a bit by avoiding unnecessary inline functions

So I was looking at the disgusting size of the git binary, and even with
the debugging removed, and using -Os instead of -O2, the size of the text
section was pretty high. In this day and age I guess almost a megabyte of
text isn't really all that surprising, but it still doesn't exactly make
me think "lean and mean".

With -Os, a surprising amount of text space is wasted on inline functions
that end up just being replicated multiple times, and where performance
really isn't a valid reason to inline them. In particular, the trivial
wrapper functions like "xmalloc()" are used _everywhere_, and making them
inline just duplicates the text (and the string we use to 'die()' on
failure) unnecessarily.

So this just moves them into a "wrapper.c" file, getting rid of a tiny bit
of unnecessary bloat. The following numbers are both with "CFLAGS=-Os":

Before:
	[torvalds@woody git]$ size git
	   text	   data	    bss	    dec	    hex	filename
	 700460	  15160	 292184	1007804	  f60bc	git

After:
	[torvalds@woody git]$ size git
	   text	   data	    bss	    dec	    hex	filename
	 670540	  15160	 292184	 977884	  eebdc	git

so it saves almost 30k of text-space (it actually saves more than that
with the default -O2, but I don't think that's necessarily a very relevant
number from a "try to shrink git" standpoint).

It might conceivably have a performance impact, but none of this should be
_that_ performance critical. The real cost is not generally in the wrapper
anyway, but in the code it wraps (ie the cost of "xread()" is all in the
read itself, not in the trivial wrapping of it).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>