Fix #1331: Emit SPV_GOOGLE_hlsl_functionality1 for counters.

It was missing when there were no semantics.
diff --git a/SPIRV/GlslangToSpv.cpp b/SPIRV/GlslangToSpv.cpp
index 1434cba..6a28a1c 100755
--- a/SPIRV/GlslangToSpv.cpp
+++ b/SPIRV/GlslangToSpv.cpp
@@ -1279,8 +1279,10 @@
                         id = getSymbolId(it->second);
                         if (id != spv::NoResult) {
                             spv::Id counterId = getSymbolId(symbol);
-                            if (counterId != spv::NoResult)
+                            if (counterId != spv::NoResult) {
+                                builder.addExtension("SPV_GOOGLE_hlsl_functionality1");
                                 builder.addDecorationId(id, spv::DecorationHlslCounterBufferGOOGLE, counterId);
+                            }
                         }
                     }
                 }