On current hardware this generally only makes a difference for vertex
textures. This fixes a regression introduced by commit
c6232e1d.

wined3d: Use the display format if WINED3DFMT_UNKNOWN is passed as backbuffer format for windowed mode resets.

win2k supports it, winxp gives one error, vista+ gives another. This
isn't interesting behavior to test.

Analogous to the light() function in state.c, the correct ModelView
matrix has to be loaded when glLightfv is called.