Add alloc_size for libiberty memory allocation functions.

2019-06-10  Martin Liska  <mliska@suse.cz>

	* ansidecl.h:
	(ATTRIBUTE_RESULT_SIZE_1): Define new macro.
	(ATTRIBUTE_RESULT_SIZE_2): Likewise.
	(ATTRIBUTE_RESULT_SIZE_1_2): Likewise.
	* libiberty.h (xmalloc): Add RESULT_SIZE attribute.
	(xrealloc): Likewise.
	(xcalloc): Likewise.

From-SVN: r272109