Add pdsg (palladium spirv-generator)

- remove glslang from pd-system
- use spirv blobs instead of glsl 460
- Use Legacy shaders for OpenGL2 backend
- add devnotes

tools/pdsg/include/spirv-helper.hpp

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+struct TBuiltInResource;
+class SpirvHelper {
+ public:
+  enum class Format {
+    GLSL,
+    HLSL,
+    MSL,  // Not supported yet
+    SPIRV,
+  };
+
+  enum class Stage {
+    Vertex = 0,
+    Geometry = 3,
+    Fragment = 4,
+  };
+
+  SpirvHelper() = default;
+  ~SpirvHelper() = default;
+
+  static void Init();
+  static void Finalize();
+  static void SetupResources(TBuiltInResource& resources);
+  static std::vector<unsigned int> GLSL2SPV(Stage stage, const char* code);
+  static std::string SPV2GLSL(const std::vector<unsigned int>& spirv,
+                              int version, bool es = false);
+  static std::string SPV2HLSL(const std::vector<unsigned int>& spirv,
+                              int version);
+};