Remove x86 jump elimination.  This was just complicated enough to make it annoying to support short jump encoding.  I measured a code size increase of 5 bytes on the V8 benchmark, from missing one jump to next elimination possibility.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@393 ce2b1a6d-e550-0410-aec6-3dcde31c8c00