Fixes warning C4806 of MS VisualC++ 6.0:
Fixes warning C4806 of MS VisualC++ 6.0:

   '&' : unsafe operation: no value of ttype 'bool' promoted to type

Done by Joachim Tesch.

Alexpux/Coin3D,Alexpux/Coin3D,Alexpux/Coin3D,Alexpux/Coin3D