This way it is way clearer what each viewport state is. There is
no more save and reset. The scissor test is also saved per
framebuffer.
The only rule to remember is that the viewport state (size and
origin) is reset for both the viewport and scissor when a texture
is attached or detached from an attachment slot.
This fix a GL_INVALID_VALUE error on startup due to 0.0f max line width.
Also moves the max anisotropy filter to the sampler creation.
This reduces code fragmentation.
