This MR extends the `wgl_pixel_format` struct with extra fields required to implement `wglGetPixelFormatAttribivARB` in opengl32.dll. I have added only fields that are relevant to the current needs of the drivers. The default implementation will be used automatically if the driver populates the extra fields, which this MR does for the winex11 driver.
The new winex11 implementation tries to remain faithful to the previous behavior in terms of error handling and fallbacks. To achieve this the `wgl_pixel_format` extra fields can be marked as invalid in order for the default implementation to return errors accordingly. Note, however, that error handling around `glXGetFBConfigAttrib` is not very consistent (e.g., the parts of `describe_pixel_format` dealing with PIXELFORMATDESCRIPTOR generally disregard errors).
The MR also adds a default implementation for `wglGetPixelFormatAttribfvARB` which piggy-backs on the integer variant of this function, and removes the need for the corresponding code in the drivers. Note that we could potentially remove this function completely from `struct opengl_funcs` (i.e., place it in `manual_win_functions` in `make_opengl`), but it seems the pattern is to maintain a complete list of extension functions (and wined3d also populates the field internally, although it doesn't seem to do anything with it).
Finally, the `winex11.drv/opengl.c` file contains a mix of coding styles. I chose to be consistent with the style of the closest context (e.g., the function) I was making changes/additions in.
-- v3: winex11: Use default wglGetPixelFormatAttribivARB implementation. winex11: Pass wgl_pixel_format to describe_pixel_format. winex11: Update describe_pixel_format coding style. opengl32: Add default implementation for wglGetPixelFormatAttribfvARB. opengl32: Add default implementation for wglGetPixelFormatAttribivARB.