[opaque pointer types] Pass function types for runtime function calls.

Emit{Nounwind,}RuntimeCall{,OrInvoke} have been modified to take a
FunctionCallee as an argument, and CreateRuntimeFunction has been
modified to return a FunctionCallee. All callers have been updated.

Additionally, CreateBuiltinFunction is removed, as it was redundant
with CreateRuntimeFunction after some previous changes.

Differential Revision: https://reviews.llvm.org/D57668

llvm-svn: 353184
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 77be915..330b876 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -2915,7 +2915,7 @@
   }
   B.addAttribute(llvm::Attribute::UWTable);
 
-  llvm::Value *Fn = CGF.CGM.CreateRuntimeFunction(
+  llvm::FunctionCallee Fn = CGF.CGM.CreateRuntimeFunction(
       FnType, FnName,
       llvm::AttributeList::get(CGF.getLLVMContext(),
                                llvm::AttributeList::FunctionIndex, B),