PR middle-end/59860
	* tree.h (fold_builtin_strcat): New prototype.
	* builtins.c (fold_builtin_strcat): No longer static.  Add len
	argument, if non-NULL, don't call c_strlen.  Optimize
	directly into __builtin_memcpy instead of __builtin_strcpy.
	(fold_builtin_2): Adjust fold_builtin_strcat caller.
	* gimple-fold.c (gimple_fold_builtin): Handle BUILT_IN_STRCAT.

From-SVN: r206848