wgl: wglChooosePixelFormatARB returns the total number of matching pixelformats and not the number of pixelformats stored in the buffer.

This didn't work due to bugs in wglChoosePixelFormatARB but also due
to strange behavior of glXChooseFBConfig. Some of its default values
are not zero or GLX_DONT_CARE which cause some formats not to appear.

This reverts commit 978f6b98.

This reverts commit b3a660a6.