Fix PR3994: LLVMMatchType arguments do not refer to absolute return value

and argument positions but only to the overloaded intrinsic parameters.
Keep a separate list of these overloaded parameters in CodeGenTarget.cpp
so they can be resolved easily.  Remove assertions from IntrinsicEmitter.cpp:
they were harmless but confusing, and the assertions elsewhere in TableGen
will catch any incorrect values.

llvm-svn: 69316