[silgen] Make ensurePlusOne emit copies even when guaranteed normal arguments is not enabled.

I want to use this to fix issues around us forwarding +0 values into memory.
These fixes are good even from the perspective of normal compilation.

rdar://34222540

Author: gottesmm

lib/SILGen/ManagedValue.cpp

@@ -203,9 +203,7 @@ void ManagedValue::dump(raw_ostream &os, unsigned indent) const {
 
 ManagedValue ManagedValue::ensurePlusOne(SILGenFunction &SGF,
                                          SILLocation loc) const {
-  // guaranteed-normal-args-todo: We only copy here when guaranteed normal args
-  // are explicitly enabled. Otherwise, this always just returns self.
-  if (SGF.getOptions().EnableGuaranteedNormalArguments && !hasCleanup()) {
+  if (!hasCleanup()) {
     return copy(SGF, loc);
   }
   return *this;