Install headers

Must be applied after the associated hhvm commit "Don't require full
source tree for building DSOs".
Merge pull request #1 from tomkwok/master

Update libsqlite3
Revert "Update libsqlite3"

This reverts commit e7bc03023a1b0311cabdb4272894453cc188e866.

Closes #4
Merge pull request #3 from tstarling/install-headers

Install headers
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
add a pthread time lock shim
add system-agnostic time functions
implement __GNUC_PREREQ/__GLIBC_PREREQ on systems that don't have it