Fix Issue 21208 - C/C++ header generation for {string,enum} enums

[wilzbach]

Split-off from #11575

[dlang-bot]

Thanks for your pull request, @wilzbach!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	21208	normal	[ICE] dtoh with enums

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#11642"

[Geod24]

Could you add a test for:

struct Foo { int i; }
enum MyEnum { A = Foo(42), B = Foo(84) }

Otherwise LGTM

[wilzbach]

Could you add a test for:

struct Foo { int i; }
enum MyEnum { A = Foo(42), B = Foo(84) }

Otherwise LGTM

Sure. Added.

[wilzbach]

@thewilsonator FYI: I added another test to cover both cases Foo being extern(D) and extern(C++).

[thewilsonator]

I'll leave merging to you then.

[wilzbach]

This doesn't make much sense, but I added it to check that there's at least no segfault.