Support for qRecover in TH with -fexternal-interpreter

Authored by simonmar.

Description

Support for qRecover in TH with -fexternal-interpreter

Summary: This completes the support for TH with -fexternal-interpreter.

Test Plan: validate

Reviewers: bgamari, ezyang, austin, niteria, goldfire, erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1748

GHC Trac Issues: Trac #11100