Impure libraries ???

[Araq]

The dependency to PCRE is IME not much of a problem (but then see the thread 
about "doesn't work at compile-time nor in NimScript"), the problem is that we 
have both `nre` and `re` and both are flawed. But maybe it is the better idea 
to patch nre and "deprecate" re. Whatever "deprecate" even means -- I cannot 
rewrite all the code that I have that uses `re`.