* app/composite/make-install.py: migrated to new (trimmer) code and
  removed dead code.  Some beautification for generated code.

* app/composite/gimp-composite-{mmx,sse,sse2,3dnow,altivec,vis,generic}.{c,h}:
  All init() functions are also a run-time check and now expected to
  return TRUE/FALSE if the particular set of compositing functions can
  be used.

* app/composite/gimp-composite.c: No longer has to determine if
  the particular set of compositing functions can be used.

* app/composite/gimp-composite-{mmx,sse,sse2,3dnow,altivec,vis}-{install,test}.c:
  Regenerated

* app/composite/test-composite.c: Deprecated, removed.  All tests are automatically
  generated and the code is in app/composite/gimp-composite-{mmx,sse,sse2,3dnow,altivec,vis}-test.c:

* app/composite/Makefile.am: removed unused references to test-composite.c