Now stack reallocate blocs of stack. If no new block needed just set new
stack_sz

Memory leak : now free stack
mem_sz op : bad size was given to bzero
sub op : handling underflow case and preparing signed int handling

Allowing copy

Now have separated tests for CTurmit and Turmit

Now we can specify a printf filename format and the save is made by PIL.
The image is build from array in main thread (avoid overhead of sending the
array through a pipe) and then saved by a Pool.

Add a correction to ensure that fractdim score is in [0..1]. The new
score in given by 1 - (1/((x+1)**4)) with x the old factdim score (between
[0..2] or [0..4] ).

Now the collect interval is incremented at each dirvar update

By compiling code on the fly and falling back to std method for jumps

Turmit stack size was 0 sometimes
Mutator sometimes delete leading to empty expressions