[OMPT] Fix test tasks/serialized.c with optimization

The compiler inlines the user code in the task. Check for that case at
runtime by comparing the frame addresses and print the expected exit
address.

Also showcase how I think the OMPT tests could be reformatted to match
LLVM's code style. In my opinion it would be great to that kind of change
to all tests that need to be touched for whatever reason...

Differential Revision: https://reviews.llvm.org/D43191

llvm-svn: 325921