RT2301: GetDIBits, not GetBitmapBits in rand_win

GetDIBits has been around since Windows2000 and
BitBitmapBits is an old Win16 compatibility function
that is much slower.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit 99b00fd99330afb0be46265c3e28f25f938d3221)