Update php-memcached to 2.1.0

Changes in 2.1.0:
- Drop support for libmemcached 0.x series, now 1.0.x is required
- Add support for virtual bucket distribution
- Fix compilation against PHP 5.2
Update php-oauth to 1.2.3.

Changes in 1.2.3:
- Fix reference counts not being incremented in OAuthProvider
Update php-http to 1.7.5.

Changes in 1.7.5:
* Fixed Bug #64310 (weak etags W/"abc" are quoted as "W/"abc"")

Changes in 1.7.4:
* Fixed Bug #61372 (build fails with "undefined symbol Z_ADDREF_P)