Use gcc auto-dependency information for lwlib and oldXMenu

Use gcc auto-dependency information for lwlib and oldXMenu

* configure.ac (lwlib_deps_frag, oldxmenu_deps_frag): New output files.

* make-dist (lwlib, oldXMenu): Distribute *.mk.

* lwlib/Makefile.in: Move old dependency information to new file deps.mk.
(MKDIR_P, DEPFLAGS, MKDEPDIR, lwlib_deps_frag):
New, set by configure.
(DEPDIR): New variable.
(ALL_CFLAGS): Add DEPFLAGS.
(.c.o): Add MKDEPDIR.
(clean, mostlyclean): Delete DEPDIR.

* lwlib/deps.mk, lwlib/autodeps.mk: New files.

* oldXMenu/Makefile.in: Move old dependency information to new file deps.mk.
(MKDIR_P, DEPFLAGS, MKDEPDIR, oldxmenu_deps_frag):
New, set by configure.
(DEPDIR): New variable.
(ALL_CFLAGS): Add DEPFLAGS.
(.c.o): Add MKDEPDIR.
(clean, mostlyclean): Delete DEPDIR.

* oldXMenu/deps.mk, oldXMenu/autodeps.mk: New files.

* src/deps.mk: Comment update.

* .bzrignore: Ignore lwlib/deps, oldXMenu/deps.