Do not allow recursive calls to vasm.

Summary: Not all callsites of Vauto are created equal, in terms of what
registers they grant Vauto to use when emitting code. This removes
the callsites that can be entered recursively from vasm itself.

Reviewed By: @swtaarrs

Differential Revision: D1614832
Split bindcall and nativecall

Summary: emitBindCall() is essentially two different things rolled into one;
Split out the case for a direct call to a NativeCall function.

Reviewed By: @maksfb

Differential Revision: D1616115
Hide temporary state used in Typing_compare

Summary: Also add an mli file for Typing_compare.

This makes it easier to figure out where state gets used.

Reviewed By: @jwatzman

Differential Revision: D1613898
Make is_hh_file a local non-reference

Summary: global references increase likelihood of save / restore flakiness

Reviewed By: @jwatzman

Differential Revision: D1613872
Refactor daemonization code.

Summary: Looks nicer to me this way; separates daemonization code from what to
do after daemonization

Reviewed By: @jwatzman

Differential Revision: D1613866