2005-07-31  Manish Singh  <yosh@gimp.org>

        * acinclude.m4
        * m4macros/Makefile.am
        * m4macros/detectcflags.m4: new macro: GIMP_DETECT_CFLAGS; used
        to detect which of a set of compiler options a compiler supports.

        * configure.in: use the above for the altivec and -fno-strict-aliasing
        flags. Also, use it to detect the presence of -mmmx and -msse, since
        those are needed to compile even MMX/SSE assembly with gcc 4.0. Define
        MMX/SSE_EXTRA_CFLAGS.

        * app/composite/Makefile.am: compile each of the composite flavors
        into their own library, so we can use automake's per-target CFLAGS.
        Use MMX/SSE/ALTIVEC_EXTRA_CFLAGS in the appropriate places. Build
        libappcomposite.a out of the resulting objects.

        * app/composite/gimp-composite-3dnow.c
        * app/composite/gimp-composite-altivec.c
        * app/composite/gimp-composite-mmx.c
        * app/...