Remove decls for rCGxxx, give them to vasm and use vasm temps instead.

Summary: Baby step towards vasm register allocation for the full unit.

Reviewed By: @alexmalyshev

Differential Revision: D1519393
Clarify error message when Hack syntax is used in a PHP file

Summary: EnableHipHopSyntax is no longer what people should probably be
enabling -- they probably want to just be using a Hack file instead.

The failure mode here can be really confusing, e.g.,
http://stackoverflow.com/questions/25496687/setting-enablehiphopsyntax-to-true-with-hhvm

Reviewed By: @elgenie

Differential Revision: D1519619
Manpage for hh_server

Summary: Debian wants these.

Reviewed By: @elgenie

Differential Revision: D1512680