Add 'lifetime' and 'type parameter list' fragment specifiers to macro parser.

[brendanzab]

This would make manipulating type parameter lists much easier.

[pnkfelix]

cc me

[tomjakubowski]

cc moi

[kmcallister]

Sigh, I guess this is another problem with using the not-actually-delimiters < and > for type parameters. If they were real delimiters you could do

(... < $($x:tt)* > ...) => ...

but this will (I think) try to consume the terminating > as another $x:tt match.

There is probably a way to fix that with a recursive macro that eats one tt at a time, and checks for > first, but bleh.

[steveklabnik]

triage: not aware of any change here.

[Mark-Simulacrum]

This is now only tracking the type parameter fragments, which would definitely need an RFC. Lifetimes in macros are tracked here: #10413. I'm going to close this since there's nothing left to be tracked in the rust-lang/rust repo for this issue.