fix compilation with Centos 5.8

LifoSem and MemoryIdler use detail/Futex.h (Futex had been disabled already) that don't compile at Centos 5.8 - Linux 2.6.18 , because FUTEX_WAIT_BITSET, FUTEX_WAKE_BITSET, FUTEX_CLOCK_REALTIME aren't defined
Merge pull request #1 from oprudkyi/centos_58

fix compilation with Centos 5.8
Merge pull request #5 from oprudkyi/centos_58

fix compilation with Centos 5.8
fix compilation with Centos 5.8

wangle/ThreadGate depends at folly/detail/Futex.h and isn't used in hhvm
Merge pull request #6 from oprudkyi/centos_58

fix compilation with Centos 5.8
Defer evaluation of CMAKE_INSTALL_PREFIX

Per #2765. This change should not be needed to close the bug, but it's
probably a good idea.
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
Update folly commit in HHVM OSS third-party

Summary: D1370893 requires folly code (`Format.h::sformat`) that is only available in a commit greater than the one pinned to the third-party folly submodule HEAD. Let's update it.

Test Plan: D1370893 will compile in open source.

Reviewers: sgolemon, liranuna, fredemmott, ptarjan

Reviewed By: ptarjan

Subscribers: folly@lists

Differential Revision: https://phabricator.fb.com/D1384493
Fix misuse of memcmp() where strcmp() was intended

This is a partial backport of http://www.sqlite.org/cgi/src/vinfo?name=d73435587b

It fixes an ASan error that HHVM routinely hits, if HHVM is patched to
use malloc() for smart_alloc(), along the lines of
https://github.com/tstarling/hiphop-php/tree/asan
Merge pull request #12 from tstarling/memcmp-unix-excl

Fix misuse of memcmp() where strcmp() was intended
Update folly submodule