Since x264-svn is more or less working a x264 USE flag could be added to vlc.
Created attachment 81501 [details, diff] Patch: adds x264 USE flag
Did you actually test it? It fails to compile here because of API mismatch. Also, x264 does not build the required .so file, just a .a one, and that makes us unable to build it as a plugin, thing that is needed to avoid breaking the whole VLC if x264 is broken.
I compiled both several times on two computers: no problem at all. Decodes and encodes h.264 perfectly.
Err okay I mixed the versions, should wake up better before thinking why I did something, sorry :P The failure here was not for API mismatch with recent VLC, but rather with PIC mismatch, and that relates with the missing .so ..