Added dev-php/hiphop-php (HipHop VM v2.1.0-dev)

https://github.com/facebook/hiphop-php
Added dev-libs/libdwarf (hiphop-php dependency)

http://reality.sgiweb.org/davea/dwarf.html
Added dev-libs/libmemcached-1.0.7 (hiphop-php dependency)

http://libmemcached.org/libMemcached.html