[CodeGen] Move `emitConstant` from ScalarExprEmitter to CodeGenFunction. NFC.

The goal is to use `emitConstant` in more places. Didn't move
`ComplexExprEmitter::emitConstant` because it returns a different type.

Reviewers: rjmccall, ahatanak

Reviewed By: rjmccall

Subscribers: dexonsmith, erik.pilkington, cfe-commits

Differential Revision: https://reviews.llvm.org/D53725

llvm-svn: 345897
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index d5de0a0..f6b7629 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -3524,6 +3524,7 @@
 
   ConstantEmission tryEmitAsConstant(DeclRefExpr *refExpr);
   ConstantEmission tryEmitAsConstant(const MemberExpr *ME);
+  llvm::Value *emitScalarConstant(const ConstantEmission &Constant, Expr *E);
 
   RValue EmitPseudoObjectRValue(const PseudoObjectExpr *e,
                                 AggValueSlot slot = AggValueSlot::ignored());