Generalize debug info test to be resilient to changes in metadata node numbering

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177238 91177308-0d34-0410-b5e6-96231b3b80d8
Split out filename & directory from DIFile to start generalizing over DIScopes

This is the first step to making all DIScopes have a common metadata prefix (so
that things (using directives, for example) that can appear in any scope can be
added to that common prefix). DIFile is itself a DIScope so the common prefix
of all DIScopes cannot be a DIFile - instead it's the raw filename/directory
name pair.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177239 91177308-0d34-0410-b5e6-96231b3b80d8
Reduced dont-infinite-loop-during-block-escape-analysis.ll with bugpoint and moved it to retain-block-escape-analysis.ll.

*NOTE* I verified that the original bug behind
dont-infinite-loop-during-block-escape-analysis.ll occurs when using opt on
retain-block-escape-analysis.ll.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177240 91177308-0d34-0410-b5e6-96231b3b80d8
Fix the build broken in r177239

Seems some accidental C++11 crept in there. Reported by the C++98 buildbots.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177241 91177308-0d34-0410-b5e6-96231b3b80d8