adding a "force-loc" field onto s-lam and s-method (though it's not
needed on s-method at the moment), and exposing location-forcing
arity-catchers and p\lambda and p\mu constructions that take an explicit
location to blame at runtime, rather than asking for (get-top-loc).
The desugaring of cases expressions is modified to create
location-forcing s-lams, with the result that arity errors in cases
are now reported at the location of the case branch, rather than the
data type
forgot to use the loc...
Undoing most of the changes (and getting rid of the force-loc fields),
and refactoring into a s-hint-exp AST node type.  This will allow
various different hint types, which we can expand as needed or
desired.  For now, the only hint is h-use-loc, which lets us specify
the location to be used when reporting arity mismatches when calling a
function.
v2
Merge branch 'master' into cases-locs
parameterize the printing of hints, and make the leftover print in
compilation become an error
Merge branch 'cases-locs' of github.com:brownplt/pyret-lang into cases-locs