Revert "Treat banged bindings as FunBinds"

Authored by bgamari on May 12 2017, 3:59 PM.

Description

Revert "Treat banged bindings as FunBinds"

This partially reverts commit 372995364c52eef15066132d7d1ea8b6760034e6 as it
doesn't actually fix Trac #13594. Namely it does not revert the mkPrefixFunRhs
refactoring since this is rather independent from the functional changes.

Going to try again with a whole working patch