Verify that calling conventions match function prototype.

Verify that calling conventions match function prototype.
This only rejects mismatches between target specific calling convention
and C/LLVM specific calling convention.
There are too many fastcc/C, coldcc/cc42 mismatches in the testsuite, these are
not reject by the verifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72248 91177308-0d34-0410-b5e6-96231b3b80d8