Add some support for readline.

Summary: I think it would be nice to move parts of hphpd over to PHP-land, and having readline available would help with that.

Reviewed By: @ptarjan

Differential Revision: D1538831
Attempt to fix t5058784

Summary: Avoid a possible race condition with static properties

Reviewed By: @markw65

Differential Revision: D1547427
Fix cmake jemalloc check

Summary: Escaped backslashes or it will fail with "unexpected CAL_symbol, expecting $end"
See 28108aeb
Closes https://github.com/facebook/hhvm/pull/3716

Reviewed By: @sgolemon

Differential Revision: D1547302
Remove some modifications in tests from import_zend_test.py

Summary: These are all invalid now.
Closes https://github.com/facebook/hhvm/pull/3717

Reviewed By: @sgolemon

Differential Revision: D1547305