Implement the extension GL_EXT_spirv_intrinsics

- Add support of SPIR-V execution mode qualifiers.
- Add support of SPIR-V storage class qualifier.
- Add support of SPIR-V decorate qualifiers.
- Add support of SPIR-V type specifier.
- Add support of SPIR-V intruction qualifiers.
- Add support of spirv_by_reference/spirv_literal parameter qualifier.
- Add shader stage macros introduced by this extension.

Test/spv.intrinsicsSpirvByReference.vert

@@ -0,0 +1,21 @@
+#version 450 core
+
+#extension GL_EXT_spirv_intrinsics: enable
+
+spirv_instruction (set = "GLSL.std.450", id = 35) // modf
+float modf(float x, spirv_by_reference float i);
+
+layout(location = 0) in float floatIn;
+layout(location = 0) out vec2 vec2Out;
+layout(location = 1) out float floatOut;
+
+void func(spirv_by_reference float f)
+{
+    f = 0.5;
+}
+
+void main()
+{
+    vec2Out.x = modf(floatIn, vec2Out.y);
+    func(floatOut);
+}