Move sandbox bytecode generation out of HPHPc

Move sandbox bytecode generation out of HPHPc

Summary:
Some of the logic to parse and produce bytecode in sandbox mode was in
compiler/analysis/emitter.cpp. There's no longer any need for it to be
there. Move it into runtime/vm/runtime-compiler.cpp instead. We no
longer need the g_hphp_compiler_parse hook, as that existed solely to
allow the runtime to call into the HPHPc code.

Instead of exposing BuiltinSymbols and AnalysisResult to the whole
world, add similar functionality for tracking systemlib unit-emitters
to systemlib.cpp. This lets us delete BuiltinSymbols entirely. There's
now no longer any dependency on compiler/ from the runtime.

Reviewed By: jano

Differential Revision: D35171055

fbshipit-source-id: 4673cc4703b40f43ed2cf048627cb6e34076886e