Remove internals for typedef declaration

[9rnsr]

Supplemental PR for the change: #4029

This PR also make the syntax is(T == typedef) an error. To do it, this PR needs corresponding Phobos fix:
dlang/phobos#2577

[9rnsr]

Also needs druntime tweaking: dlang/druntime#978

[quickfur]

Looks like druntime and phobos are ready for this now. Time to merge?

[9rnsr]

Yes, ready to merge.

[ibuclaw]

I'm ready for this. Any last objections @WalterBright, @andralex?

[dnadlinger]

Was the is(T == typeof) syntax marked as deprecated before? If not, can we keep it around as deprecated and hard-coded to false for a couple of releases or so?

[9rnsr]

Was the is(T == typeof) syntax marked as deprecated before? If not, can we keep it around as deprecated and hard-coded to false for a couple of releases or so?

Surely immediate error was not good. I made the is(T == typeodef) syntax deprecated.

[WalterBright]

Let me take a look at this after I get home. Thanks!

[dnadlinger]

@WalterBright: When would that be, approximately? The PR should be good to go, although the is(T == typedef) deprecation message could maybe be a bit more explanatory as to what the user needs to do to fix their code (no good ideas, unfortunately).

[WalterBright]

The break; has become dead code.

[9rnsr]

Right, fixed.

[WalterBright]

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