Permit lifetimes to appear in type parameter lists and after `&`.  Lifetimes in
type parameter lists are currently ignored, but `&'a T` is equivalent to
`&a/T`.
emacs mode: Highlight 'foo as a lifetime, not a character constant.
Make 'foo use font-lock-builtin-face, like module names, and make capitalized identifiers optionally use font-lock-type-face
Parse (and discard) lifetime declarations on function types