Web: Selectively remove a few key features, using #ifndef GLSLANG_WEB

Save about 100K.

N.B.: This is done by eliminating a function call, at a high level,
not by #ifdef'ing a bunch of code.

Also, removed no longer needed *_EXTENSION #ifdef in the code not
needed by GLSLANG_WEB.

SPIRV/SpvBuilder.cpp

@@ -2089,6 +2089,7 @@ Id Builder::createTextureQueryCall(Op opCode, const TextureParameters& parameter
     if (parameters.lod)
         query->addIdOperand(parameters.lod);
     buildPoint->addInstruction(std::unique_ptr<Instruction>(query));
+    addCapability(CapabilityImageQuery);
 
     return query->getResultId();
 }