* regex.c (EXTEND_BUFFER): Adjust pointers within buffer by

	* regex.c (EXTEND_BUFFER): Adjust pointers within buffer by
	computing their offset from the start of the old buffer and adding
	to the new buffer, rather than by assuming we can add the
	difference between the old buffer and the new buffer (it might not
	fit in an int).  Merge in cosmetic differences from emacs regex.c
	version of this macro.