Add backends

- Renamed GfxOpenGL to GfxOPenGL2
- Added GfxOpenGL3 backend for OpenGL 3.3+
- Added WIP DirectX9 backend
- Added structure for Citro3D
- Added linear Allocator

include/pd/lithium/pools.hpp

@@ -5,8 +5,8 @@
 
 namespace PD {
 namespace Li {
-void InitPools(size_t max_vertices = 32768);
-Vertex* AllocateVertices(size_t count);
-u16* AllocateIndices(size_t count);
+PD_API void InitPools(size_t max_vertices = 32768);
+PD_API Vertex* AllocateVertices(size_t count);
+PD_API u16* AllocateIndices(size_t count);
 }  // namespace Li
 }  // namespace PD