[OpaquePtr] Support call instruction

Add support for call of opaque pointer, currently only possible for
indirect calls.

This requires a bit of special casing in LLParser, as calls do not
specify the callee operand type explicitly.

Differential Revision: https://reviews.llvm.org/D104740

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -5266,7 +5266,7 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
             cast<PointerType>(Callee->getType())->getElementType());
         if (!FTy)
           return error("Callee is not of pointer to function type");
-      } else if (cast<PointerType>(Callee->getType())->getElementType() != FTy)
+      } else if (!OpTy->isOpaqueOrPointeeTypeMatches(FTy))
         return error("Explicit call type does not match pointee type of "
                      "callee operand");
       if (Record.size() < FTy->getNumParams() + OpNum)