Add extra break statements to quiet clang warnings.

Clang complains about code that falls through into an empty default
case, so add some breaks to placate it.

glslang/HLSL/hlslGrammar.cpp

@@ -391,6 +391,7 @@ bool HlslGrammar::acceptDeclaration(TIntermNode*& nodeList)
     case EvqOut:
     case EvqInOut:
         parseContext.error(token.loc, "in/out qualifiers are only valid on parameters", token.string->c_str(), "");
+        break;
     default:
         break;
     }