[Exception Handling] Unwind tables are required for all functions that have an EH personality.

This patch is for defect:
https://bugs.llvm.org/show_bug.cgi?id=32611

Functions may require unwind tables even if they are marked with the attribute
nounwind. Any function with an EH personality may require an unwind table.

Differential Revision: https://reviews.llvm.org/D50987

llvm-svn: 340641