builtins.c (fold_builtin_memcpy, [...]): New functions.

	* builtins.c (fold_builtin_memcpy, fold_builtin_mempcpy,
	fold_builtin_memmove, fold_builtin_strcpy, fold_builtin_strncpy,
	fold_builtin_memcmp, fold_builtin_strcmp, fold_builtin_strncmp):
	New functions.
	(expand_builtin_memcpy): Use integer_zerop instead of testing
	host_integerp and tree_low_cst directly.  Move misapplied hunk
	for optimization wher SRC and DEST point to the same location.
	(expand_builtin_mempcpy): From here.
	(expand_builtin_memmove): Use integer_zerop instead of testing
	host_integerp and tree_low_cst_directly.
	(expand_builtin_memset): Likewise.
	(expand_builtin_memcmp): Likewise (and for integer_onep).
	(expand_builtin_strncmp): Likewise.
	(fold_builtin): Call the appropriate fold_builtin_foo functions
	to optimize memcpy, mempcpy, memmove, strcpy, strncpy, memcmp,
	strcmp and strncmp.

From-SVN: r72547