use the 'new' alias syntax

[wilzbach]

AFAICT we should only use one alias syntax in Phobos (and hopefully deprecate the older soon).
This PR deprecates the old alias type identifier in favor of the new alias identifier = type syntax.

[JackStouffer]

LGTM

I can't believe

1. That there were still this many uses of the old syntax
2. That the old syntax still isn't deprecated

[wilzbach]

That there were still this many uses of the old syntax

There's even a bit more at typecons.d, but here it uses a FuncDeclarator. Is there a good way to replace those occurrences?

[DmitryOlshansky]

Auto-merge toggled on

[andralex]

noice