A dumb, non-working threading prototype
A very preliminary threading system. Breaks everything

Also: No BVA if threading.
Oops, typo in #define. Fixed.
Fixing memory leak
Fixing an assert
Fixing printing layout
Fixing the priting layout
Fixing some problems with shared data and cleaning up verbosity setting
Adding some commented-out printing to know what we are doing
After updating variable numbers, the order of the literals could change
More sync thread verbosity
DataSync: forgot to update variables on renumbering
Allowing multi-threading. Very dangerous, and very untested
Better variety of solvers for multi-threaded solving
Only print statistics of the thread that solved the problem
Adding interrupt and time check to probing
Adding interrupt check to search()
More checks of time, conflict and interrupt in simplify()