Make test resistant to false matches of numbered (unnamed) labels inside other numbers.

Make test resistant to false matches of numbered (unnamed) labels inside other numbers.

In release builds labels are numbers. Matching just the number may result
in false matches where the label is contained in other numbers, such as
14 inside [114 x i8]. A stricter match requiring start of line or > character
before the label avoids these false matches.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@246385 91177308-0d34-0410-b5e6-96231b3b80d8