SAW <-> Cryptol positions for Cryptol parsing

[sauclovian-g]

It seems that when SAW parses Cryptol code blocks it does this to make the positions come out:

  str = concat [ replicate (inpLine inp - 1) '\n'
               , replicate (inpCol inp - 1) ' '
               , inpText inp ]

(here)

This is correct but not particularly desirable, and should be improved someday. (However, this will need an additional set of entry points to the Cryptol parser that allow providing a start position, or something of the sort, which will also be somewhat messy.)