check float texture extension, use float32 or float16 if available, show extension on title bar, add thread and render task for lightmap rendering

src/shader.cpp

@@ -7,6 +7,8 @@
 std::map<kShader, Shader> ShaderManager::m_shaders;
 Shader* ShaderManager::m_current;
 bool ShaderManager::ext_framebuffer_fetch = false;
+bool ShaderManager::ext_texture_float = false;
+bool ShaderManager::ext_half_float_pixel = false;
 
 std::string Shader::read(const std::string& path)
 {