Fix a few memory leaks in the, most of them in error cases but one or two

Fix a few memory leaks in the, most of them in error cases but one or two

1999-07-18  Larry Ewing  <lewing@gimp.org>

	* src/io-xpm.c:
	* src/io-gif.c:
	* src/io-png.c:
	* src/io-jpeg.c: Fix a few memory leaks in the, most of them in
	error cases but one or two in the common case.  There are probably
	a few small ones left.