Front-end: Get the right set of nodes marked as spec-const.

This is according to the expected KHR_vulkan_glsl without floating point.
So, floating-point spec-const operations no longer work, and that's
reflected in the tests.

glslang/MachineIndependent/localintermediate.h

@@ -342,6 +342,8 @@ protected:
     TIntermSequence& findLinkerObjects() const;
     bool userOutputUsed() const;
     static int getBaseAlignmentScalar(const TType&, int& size);
+    bool isSpecializationOperation(const TIntermOperator&) const;
+
 
     const EShLanguage language;  // stage, known at construction time
     EShSource source;            // source language, known a bit later