Debug Info: use module flag to set up Dwarf version.

Correctly handles ref_addr depending on the Dwarf version. Emit Dwarf with
version from module flag.

TODO: turn on/off features depending on the Dwarf version.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185484 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/AsmPrinter.h

@@ -121,6 +121,8 @@ namespace llvm {
   public:
     virtual ~AsmPrinter();
 
+    const DwarfDebug *getDwarfDebug() const { return DD; }
+
     /// isVerbose - Return true if assembly output should contain comments.
     ///
     bool isVerbose() const { return VerboseAsm; }