In this commit:
* Change the lit_int_unsuffixed AST node to not carry a type, since
it doesn't need one
* Don't print "(unsuffixed)" when pretty-printing unsuffixed integer
literals
* Just print "I" instead of "(integral)" for integral type variables
* Set up trans to use the information that will be gathered during
typeck to construct the appropriate constants for unsuffixed int
literals
* Add logic for handling int_ty_sets in typeck::infer
* Clean up unnecessary code in typeck::infer
* Add missing mk_ functions to middle::ty
* Add ty_var_integral to a few of the type utility functions it was
missing from in middle::ty
While it wasn't the original issue, the first program from #2487
failed the pretty-printing test because of this, so it's still a good
test case :-)
It also turns out that the second program from #2487 now triggers a
kind error, so I figured I might as well add it as a test case.
