[IRGen] Handle 'super' method sends in ObjC partial application forwarders.

The Objective-C partial application forwarder that one gets when
using, e.g., "super.foo" as a function value was doing a normal
objc_msgSend. Fix the miscompile by threading all of the information
about the Objective-C message send through the forwarder.

Fixes rdar://problem/28140758.

lib/IRGen/GenObjC.cpp

@@ -786,7 +786,7 @@ llvm::Value *irgen::emitObjCAllocObjectCall(IRGenFunction &IGF,
 }
 
 static llvm::Function *emitObjCPartialApplicationForwarder(IRGenModule &IGM,
-                                            SILDeclRef method,
+                                                           ObjCMethod method,
                                             CanSILFunctionType origMethodType,
                                             CanSILFunctionType resultType,
                                             const HeapLayout &layout,
@@ -884,10 +884,12 @@ static llvm::Function *emitObjCPartialApplicationForwarder(IRGenModule &IGM,
   }
 
   // Prepare the call to the underlying method.
+  
   CallEmission emission
-    = prepareObjCMethodRootCall(subIGF, method, origMethodType, origMethodType,
+    = prepareObjCMethodRootCall(subIGF, method.getMethod(),
+                                origMethodType, origMethodType,
                                 ArrayRef<Substitution>{},
-                                ObjCMessageKind::Normal);
+                                method.getMessageKind());
   
   Explosion args;
 
@@ -895,7 +897,8 @@ static llvm::Function *emitObjCPartialApplicationForwarder(IRGenModule &IGM,
   if (formalIndirectResult)
     args.add(formalIndirectResult);
 
-  addObjCMethodCallImplicitArguments(subIGF, args, method, self, SILType());
+  addObjCMethodCallImplicitArguments(subIGF, args, method.getMethod(), self,
+                                     method.getSearchType());
   args.add(params.claimAll());
   emission.setArgs(args);
   
@@ -930,7 +933,7 @@ static llvm::Function *emitObjCPartialApplicationForwarder(IRGenModule &IGM,
 }
 
 void irgen::emitObjCPartialApplication(IRGenFunction &IGF,
-                                       SILDeclRef method,
+                                       ObjCMethod method,
                                        CanSILFunctionType origMethodType,
                                        CanSILFunctionType resultType,
                                        llvm::Value *self,