MaxwellToGL: Added a TODO and partial implementation of maxwell wrap mode 4 (Clamp, GL_CLAMP).

This clamp mode was removed from OpenGL as of 3.1, we can emulate it by using GL_CLAMP_TO_BORDER to get the border color of the texture, and then manually sampling the edge to mix them in the fragment shader.

src/video_core/renderer_opengl/maxwell_to_gl.h

@@ -74,6 +74,11 @@ inline GLenum WrapMode(Tegra::Texture::WrapMode wrap_mode) {
     switch (wrap_mode) {
     case Tegra::Texture::WrapMode::ClampToEdge:
         return GL_CLAMP_TO_EDGE;
+    case Tegra::Texture::WrapMode::ClampOGL:
+        // TODO(Subv): GL_CLAMP was removed as of OpenGL 3.1, to implement GL_CLAMP, we can use
+        // GL_CLAMP_TO_BORDER to get the border color of the texture, and then sample the edge to
+        // manually mix them. However the shader part of this is not yet implemented.
+        return GL_CLAMP_TO_BORDER;
     }
     LOG_CRITICAL(Render_OpenGL, "Unimplemented texture wrap mode=%u", static_cast<u32>(wrap_mode));
     UNREACHABLE();