Use distcc instead of ccache for building in benchy

Summary: This will build folly and stuff slower, but if you are benchying
something with local hphp header changes it'll probably win on build times,
since there'll be better parallelism.

Reviewed By: @mhahnenberg

Differential Revision: D1627193
Fix JSON decode constant

Summary: Fixes #4018

Reviewed By: @JoelMarcey

Differential Revision: D1626488
Have FrameState track in and out states of blocks.

Summary: Currently FrameState uses its map of snapshots to map blocks to their
in-states, except for when we're building, then we map blocks that have
already been processed to their out-state for
IRBuilder::insertLocalPhis.

To clean things up and reduce confusion, lets just store both the in and
out state for each block.

Reviewed By: @swtaarrs

Differential Revision: D1619253
Raise emitCallNativeImpl() to vasm

Summary: bindcall{} calling a native method (whose bytecode body
is just a NativeImpl) instruction emits some glue and
then a plain call, no service request. Do it all with vasm.

Reviewed By: @swtaarrs

Differential Revision: D1617362