Upload the color/stencil buffers on FBO creation.

Fixes pausing or loading a savestate in Star Ocean (previously your
character became invisible until the screen panned.)
Clear depth buffers to zero, not 1.0f.

Memory is generally initially zeros.
Clear stencil to 0, not 1.

Memory is generally initially zeros, after all.  Fixes #5205 (or at least
improves it?) and fixes #6226.