XCB: compile events.c only once (refs #9367)
PulseAudio: compile helper only once (refs #9367)
Remove left-over .gitignore files
video_chroma: avoid genmf
mmx: merge back into video_chroma (refs #9367)
sse2: merge back into video_chroma (refs #9367)
altivec: merge back into video_chroma (refs #9367)

It is a bit odd that both inline and external flags are mixed together.
This might be an old silent bug.
configure: remove stray references to memcpyaltivec
configure: expose -Bsymbolic to makefiles
avformat: avoid genmf
avcodec: move more build logic to Makefile
modules: factor Makefile statement
i420_rgb: dead code
i420_rgb: split files and clean up
codec: avoid genmf for simple audio codecs
dts: compile header helpers only once (refs #9367)