Convert E_RECOVERABLE_ERROR into RuntimeException

Summary:
We currently treat typehint violations as warnings in normal use, and only raise InvalidArgumentException via assert_instances_of(). Instead, always raise InvalidArgumentException.

E_RECOVERABLE_ERRORs are always severe; raise them all as runtime errors.

Raise "use of undefined variable" as a runtime error, it is highly correlated with badness.

Test Plan: Ran a program with undefined variables and typehint problems.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D2653