Better fix for the static property race

Summary: If two threads tried to initialize static properties
for a derived class at the same time, and both tried to initialize
same same persistent property, the second one could overwrite
the property's value with garbage.

Reviewed By: @edwinsmith

Differential Revision: D1552834
Remove Accept-Encoding header

Summary: See comments in nginx.conf.in

Reviewed By: @oyamauchi

Differential Revision: D1552856
import readline tests

Summary: We start to support readline, yey!
Relevant commit 30cb287
Closes https://github.com/facebook/hhvm/pull/3723

Reviewed By: @sgolemon

Differential Revision: D1548083