Update docstrings for UnicodeChar::is_digit => is_numeric rename
auto merge of #19348 : SimonSapin/rust/patch-9, r=huonw
Move various data structures out of typeck and into ty.
Move infer out of `middle::typeck` and into just `middle`.
Remove dependency on typeck from lint.
Remove dependence on typeck from ppaux.
Remove "dependence" on typeck from comment in substs.
Remove one dependence on typeck from const_eval.
Move `typeck` logically in the module tree out to the root and clamp
down on its exports. Remove some dead code that is revealed.
Modify libsyntax/diagnostics to not be so persnickety. The scheme
doesn't work in a multi-crate context. We'll need to come up with
something better.
Move typeck into its own crate.
Remove dependencies on driver from trans et al. by moving various
structs out from driver and into other places.
Separate the driver into its own crate that uses trans, typeck.