Have 'make' output better GEN names

Have 'make' output better GEN names

* lisp/Makefile.in (PHONY_EXTRAS): New macro.
(.PHONY): Depend on it, and on $(lisp)/loaddefs.el, so that the
relevant files' time stamps are ignored.
(custom-deps, $(lisp)/cus-load.el, finder-data)
($(lisp)/finder-inf.el): Use PHONY_EXTRAS.
(custom-deps, $(lisp)/cus-load.el, finder-data)
($(lisp)/finder-inf.el, autoloads, $(lisp)/loaddefs.el)
($(lisp)/subdirs.el, update-subdirs):
Output more-accurate destination names with GEN.
* src/Makefile.in (gl-stamp, globals.h): Simplify by putting the new
contents of globals.h into gl-stamp.  This lets us use AM_V_GEN
more naturally so that 'make' can output more-accurate names.