Merge pull request #7 from tstarling/defer-install-prefix

Defer evaluation of CMAKE_INSTALL_PREFIX
add fastlz library for ext_memcached

The PHP memcached extension (which ext_memcached emulates) uses fastlz
compression by default. A follow-up commit to hhvm/hhvm will add fastlz support
for the HHVM extension.
Merge pull request #8 from atdt/master

add fastlz library for ext_memcached
[1/2] fix thrift build on OSX