Work around some CD device stops. Oz - 'CDROMSTOP ioctl causes any ioctls following immediately to fail for a considerable time'.

git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk/quakespasm@948 af15c1b1-3010-417e-b628-4374ebc0bcbd
minor cd_sdl cleanup after r948

git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk/quakespasm@949 af15c1b1-3010-417e-b628-4374ebc0bcbd