Fixed already solved problem in perform_substitution and added a test to avoid it reappear
Minor format improvement with lists
Including the extra character nl in the boundaries of a comment, if it start with %
Minor bug fix in prolog:xref_open_source
Unify File only if it is uninstantiated
Less fail prone
Hack to avoid refactorization at the same position more than once
Updated gcb test
b_getval--->nb_current in prolog:xref_open_source/2