Make EHFrames available to sub-classes of RTDyldMemoryManager.

Summary: This information can be useful; and in the case of Win64, necessary for getting exceptions to work in the JIT.

Reviewers: lhames

Reviewed By: lhames

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D35102

llvm-svn: 308321