Freeze measurePosition while Timing.timing is off

Freeze measurePosition while Timing.timing is off

Also don't reset it in \cadenzaOff, and leave autoBeaming alone in
\cadenzaOn/\cadenzaOff.  This should cause quite fewer interferences
of cadenze with timing, accidentals, barlines and other stuff.

[Trevor Daniels, 2013-10-26 09:56:57]

Looks a better way of handling cadenze.  I like it!

Trevor