Use a separate field to keep track of allocations for the purpose of out of memory checking.

When jemalloc is used, the code for tracking out of memory situations conflicts with the code that figures out how much memory is actually in use. To solve this, I've introduced a new usage counter field in the memory manager. Presumably, this counter is less accurate than the one that is maintained by the jemalloc specific code in MemoryManager::refreshStatsImpl, but this should not matter because it's only role is to trigger an out of memory check, which is done using the usage field maintained by refreshStatsImpl. If this check is triggered, the new counter is updated to the presumably more accurate value.

Reviewed By: @edwinsmith

Differential Revision: D994503
Implement date_parse_from_format

Ended up doing a little of refactoring around DateTime too.

This is for a fatal in Laravel.

Reviewed By: @JoelMarcey

Differential Revision: D995643
Make FrozenVector a collection

Add FrozenVector as a collection.

Enable the following:
  * frozen vector literals
  * casting fvs to array and bool
  * array_key_exists and isset with fv

Reviewed By: @paroski

Differential Revision: D988612
Implement PharData::extractTo

This is needed for composer to install the dependancies for phpunit.

I also upgraded composer while I was in there.

Reviewed By: @JoelMarcey

Differential Revision: D1005174
Fix macro typo in native.h

Fix macro typo in native.h

Reviewed By: @JoelMarcey

Differential Revision: D1005290

Pulled By: @scannell
Change the block labels in prettyprint output to B instead of L.

Reviewed By: @ottoni

Differential Revision: D1005392