Clean up the tests for warning about unused function results given the
appropriate attribute. Add a bit more testing that finds a pretty bad
regression (since ~forever) in this warning. Fix it with a nice 2 line
change. =]

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@126098 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed