opengl: filters: fix BindFramebuffer target on < 3
OpenGL / OpenGL ES < 3 don't support GL_DRAW_FRAMEBUFFER and will trigger a GL_INVALID_ENUM error during runtime.
GL_DRAW_FRAMEBUFFER AND GL_READ_FRAMEBUFFER where used for MSAA resolution, which is also not available on OpenGL / OpenGL ES < 3 except extensions. The separate .can_blit member is there to:
- Replace filters->api's booleans on the long run.
- Identify what depends on the framebuffers themselves (is GL_DRAW_FRAMEBUFFER allowed?) and what enables the MSAA values from the filters.
Fix compatibility issues with OpenGL ES 2 on some Android devices.