helps with readability since these, especially named-IPi, come up a lot
didn't change everything that could need it like PiInfo or BindMode
PiInfo rarely has DefImplicit (so far) and BindMode hasn't come up a lot (so far)
reduced indentation for TTImp Show implementation
This is mostly to make it easier to write linear function types without
having to invent names for everything, which might be noisy. Also it
improves the display of linear function types when the name isn't used
in the scope.
