Some functions seem to assume that the program paths are formed by a
fully left-associative application of the Seq constructor (as in: Seq
Skip $ Seq Skip $ ... $ Seq Skip Skip). Therefore, this function is
added; it will turn any string of Seq'ed statements into this shape.
Using this function will do no harm (other than possibly spending effort
into doing nothing), so use it accordingly.

This change allows us to calculate program paths from all programs (as
long as they don't contain any try-catch). Using this, we should be able
to calculate ALL wlps for the programs. However, the checks are not
complete for the whole program, as only program paths up to a certain
length are checked. Any further program paths might say that the program
is (in)correct and give a different result.