Fix PR1816. If a bitcast of a function only exists because of a

Fix PR1816.  If a bitcast of a function only exists because of a
trivial difference in function attributes, allow calls to it to
be converted to direct calls.  Based on a patch by Török Edwin.
While there, move the various lists of mutually incompatible
parameters etc out of the verifier and into ParameterAttributes.h.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44315 91177308-0d34-0410-b5e6-96231b3b80d8