Skip the asm prefix when storing the name in block info.

Skip the asm prefix when storing the name in block info.
 - Otherwise we emit internal names with embedded '\01' characters,
   which confuses some tools.

 - Ideally all the code which wants to get a "display name" for the
   given function should follow one code path, but this should be a
   monotonic improvement for now.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@71774 91177308-0d34-0410-b5e6-96231b3b80d8