Added support for depth and stencil formats for glBlitFramebuffer:
- Blitter now supports quad layout and stencil
- Device::stretchRect() now supports specific buffers, so that a
  caller can specifically choose which buffer to copy

Change-Id: Iae0898df11e0a1d3c006113486ed15a3fd2f90a9
Reviewed-on: https://swiftshader-review.googlesource.com/7510Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>