[First Draft] Add @gc as a Function Attribute

[Dom DiSc]

On Saturday, 22 June 2024 at 04:37:01 UTC, Walter Bright wrote:
> I've been thinking about a `@default` attribute, which will 
> reset the state of attributes to the defaults. This will 
> obviate the need for @gc, @impure, @throw, and so forth.

But will bite us if we ever changing the default :-/