SPV: Emit layout(index=) as Index decoration.

SPIRV/GlslangToSpv.cpp

@@ -2393,6 +2393,8 @@ spv::Id TGlslangToSpvTraverser::getSymbolId(const glslang::TIntermSymbol* symbol
         addDecoration(id, TranslateInterpolationDecoration(symbol->getType()));
         if (symbol->getQualifier().hasLocation())
             builder.addDecoration(id, spv::DecorationLocation, symbol->getQualifier().layoutLocation);
+        if (symbol->getQualifier().hasIndex())
+            builder.addDecoration(id, spv::DecorationIndex, symbol->getQualifier().layoutIndex);
         if (symbol->getQualifier().hasComponent())
             builder.addDecoration(id, spv::DecorationComponent, symbol->getQualifier().layoutComponent);
         if (glslangIntermediate->getXfbMode()) {

SPIRV/SpvBuilder.cpp

@@ -450,7 +450,7 @@ Id Builder::findScalarConstant(Op typeClass, Id typeId, unsigned value) const
     return 0;
 }
 
-// Version findScalarConstant (see above) for scalars that take two operands (e.g. a 'double').
+// Version of findScalarConstant (see above) for scalars that take two operands (e.g. a 'double').
 Id Builder::findScalarConstant(Op typeClass, Id typeId, unsigned v1, unsigned v2) const
 {
     Instruction* constant;