Plug Unc and InitUnc RATs through to the JIT

Summary: IIRC they used to be a regression (maybe a JIT-time only issue, which
preflab isn't measuring anymore)---but it looked probably in the noise-ish now
in a perflab run.  Still leaving out OptBool and such types.

Reviewed By: @swtaarrs

Differential Revision: D1699541
Add support for --region-mode=wholecfg to hhvm_wrapper

Reviewed By: @mhahnenberg

Differential Revision: D1699777

Signature: t1:1699777:1416771111:becfb50b8ea59b21f061716028e3ee42c6f11ad7
Convert JEMALLOC_STATS_ADJUST into an inline method.

Summary: It's not that complicated. Also simplify how jemallocDebt is
declared.

Reviewed By: @bertmaher

Differential Revision: D1699860
abstract constants: adding parser support [1/2]

Summary: From the moment that PHP introduced late static binding, it
 created the possibility of `static::SOME_CONST`, which left the class
 hosting such a method with two unpalatable choices:

  * defining a default value for SOME_CONST, with the clear disadvantages
    of not having a suitable default **and** forgetful subclasses not
    overriding the default
  * not defining the default value, and incurring unexpected fatals in
    code not easily amenable to static analysis.

 This diff introduces `abstract const` to the HHVM parser, at this
 point dropped before the preclass is emitted.

Reviewed By: @paroski

Differential Revision: D1693720

Signature: t1:1693720:1416609953:06a21a13fbda5acc7d145d92e21a2d1dd53d9dbe