[SILGen] Emit toplevel code through emitFunctionDefinition

Emit SILDeclRefs representing entry points with SourceFile
source correctly.

Author: Zak Kent

lib/SILGen/SILGenTopLevel.cpp

@@ -1,3 +1,15 @@
+//===--- SILGenTopLevel.cpp - Implements Top-level Code Emission ----------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
 #include "SILGenTopLevel.h"
 #include "SILGenFunction.h"
 #include "Scope.h"