opengl: use single precision trigonometry
opengl: use single precision trigonometry

 - Use single precision trigonometric functions.
 - Compute sine and cosine only once.
 - Combine sine and cosine computation - on platforms allowing it.

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc