message: Add a missing forward declaration, second attempt
  I had misspelled DWARFCompileUnit as DWARCompileUnit.
diff: @@ -48,7 +48,7 @@ class DebugMapModule;
  class DWARFAbbreviationDeclaration;
  class DWARFAbbreviationDeclarationSet;
  class DWARFileUnit;
  -class DWARCompileUnit;
  +class DWARFCompileUnit;
  class DWARFDebugAbbrev;
  class DWARFDebugAranges;
  class DWARFDebugInfo;
  