[Gecode] NoVar novar

[Gabor Szokoli]

Hello!

gecode/int/linear/novar.hh declares a global extern NoVar instance that 
does not seem to be instantiated anywhere. As it has no state just 
non-virtual inline methods, it is not a problem at -O3, but causes 
inconvenience (linking errors) in a debug build. A quick-and-dirty 
workaround is to include this header in the example being debugged, and 
just declare the variable:

#include "int/linear/novar.hh"
NoVar novar;

Also, expressinos passed as arguments may suprise some macros, an extra 
pair of () never hurts. (Both in macro definitions and applicatoins :-) )
Just sharing my experiences, the queens example now works (at least for 
me) with CL_BND on gcc.


Gabor