Don't emit structors for available_externally globals (PR19933)

We would previously assert here when trying to figure out the section
for the global.

This makes us handle the situation more gracefully since the IR isn't
malformed.

Differential Revision: http://reviews.llvm.org/D4022

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210215 91177308-0d34-0410-b5e6-96231b3b80d8
Explain why we skip DbgInfoIntrinsics when looking at line numbers in .gcno file emission.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210218 91177308-0d34-0410-b5e6-96231b3b80d8