dpll.js: Update the tree along the dpll execution

We are using the recursion stack to update the tree. This solved t1.cnf but
I found a problem with another formula, described on t2.cnf.

Signed-off-by: Diego Pasqualin <dpasqualin@c3sl.ufpr.br>
t2.cnf: Add formula that is not working on current implementation

For some reason there is a third node coming out of Root...

Signed-off-by: Diego Pasqualin <dpasqualin@c3sl.ufpr.br>