[DebugInfo] Fix ARM/AArch64 prologue_end position. Related to D11268.

Summary:
This review is related to another review request http://reviews.llvm.org/D11268, does the same and merely fixes a couple of issues with it.

D11268 is quite old and has merge conflicts against the current trunk.
This request 
 - rebases D11268 onto the new trunk;
 - resolves the merge conflicts;
 - fixes the prologue_end tests, which do not pass due to the subprogram definitions not marked as distinct.

Reviewers: echristo, rengolin, kubabrecka

Subscribers: aemerson, rengolin, jyknight, dsanders, llvm-commits, asl

Differential Revision: http://reviews.llvm.org/D14338

llvm-svn: 252177