Add namespaced name to closures

Summary: Fixes facebook/hhvm#1669

Reviewed By: @paulbiss

Differential Revision: D1662546

Signature: t1:1662546:1415235548:93421bc3160e3dbec7aa582a14f4cd8afba83706
Yell when catching an uninstantiable class

Summary: Same check as instanceof.

Reviewed By: @elgenie

Differential Revision: D1661501

Signature: t1:1661501:1415297384:e6ff49b7f3e70b488731065ab784c81f1bce2c08
typechecker: more instantiability tests

Summary: * the typehints for class members should be checked for instantiability
 * add an optional param for testing instantiability to typing_hint

Reviewed By: @jwatzman

Differential Revision: D1663959

Signature: t1:1663959:1415299374:32bfb660288df0d661ca51c3f16749c0ba4d6fe1