Added format arguments to DepthBuffer/DepthStencilBuffer
constructors and added existing types to type conversion
functions so that more than one depth/stencil format may
be supported.

Change-Id: Ifd60b896e93a1ba4d05a30f123a1322cdd5254a5
Reviewed-on: https://swiftshader-review.googlesource.com/4766Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>