* gimp-composite-mmx-{test,installer}.c

* gimp-composite-sse-{test,installer}.c

* gimp-composite-sse2-{test,installer}.c

* make-installer.py: sort test output by mode name

* gimp-composite-sse2.[ch]: New compositing mode implementations
  darken
  difference
  grain_extract
  lighten

* gimp-composite-x86.h: added

* gimp-composite-{sse,mmx,sse2}.[ch]: Tightening declarations of clobbered registers.