added a new Config::Bind that works for ini settings

Summary: There was no good way to variables to ini settings that did not automatically enable them for config.hdf. Now there is a Config::Bind function that will bind an ini setting to a variable using the value specified in the ini file or the a given default otherwise. The main difference between this Config::Bind and the old/other one is that it does not prepend "hhvm." on the front and does not override the ini setting with a hdf setting.

D1474476 depends on this diff and had a clean run. Given that this diff runs no new code it seems safe to override failures.

Reviewed By: @ptarjan

Differential Revision: D1463584
Corrected the serialization and unserialization of DateTime

Summary: Our implementation of `__sleep` and `__wakeup` for `DateTime` were wrong. This diff brings them up to par with PHP.

Fixes #2753

Reviewed By: @ptarjan

Differential Revision: D1354608
Remove string type annotation from TarArchiveHandler::path

Summary: HHBBC is failing to infer string for this type, and it blocks
compiling the repo.  I can't find the problem in HHBBC so this is a temporary
workaround.

Reviewed By: @edwinsmith

Differential Revision: D1485401
Initialize memory manager before using it

Summary: A recent re-shuffle of when the thread locals get initialized
on the main thread caused an issue with trying to allocate Strings
before initializing the memory manager.

Reviewed By: @bertmaher

Differential Revision: D1485657
Let status.php response from HHVM include host health level.

Summary: Let the return dictionary of apache_get_config also include
the local host level.

Reviewed By: dmitrip

Differential Revision: D1472139
make calendar_getNow_basic.php less strict

Summary: It failed once in D1479620?id=4763805

Reviewed By: @JoelMarcey

Differential Revision: D1486405