Declare class DwarfDebug before use instead of relying on a forward declaration

from some other unrelated header.

Patch by Kai.

llvm-svn: 170284

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -41,6 +41,7 @@ class DIEAbbrev;
 class DIE;
 class DIEBlock;
 class DIEEntry;
+class DwarfDebug;
 
 //===----------------------------------------------------------------------===//
 /// \brief This class is used to record source line correspondence.