Fixes #697, #899 and possibly #341: Rail width rounding issues

As documented in issues #697 and #899 and probably #341, in some situations the fullscreen button gets pushed off the end of the control bar. This is the result of the time rail being 1px to large, caused by rounding of the decimal value for the time rail's width that is generated by the player at various player widths.

 I've found that the easiest solution is simply to just modify the rail width calculation to subtract 1px from the rail's width to account for any problems.