checked wishnu's mutations and applies manual preprocessing/desugaring where needed. Also fixed a bug where introduced variables in the wlp would result in an error (introduced variables may be part of the wlp when the code contains non-void functions that don't terminate within the set limit of iterations)

added special syntax to reason about the return value of methods in the post condition, added some equivalent mutants (c# code), changed while loops to generate smaller wlp formulas if the loop does not affect the post condition