ABI-specific integers

[dcharkes]

A copy of c_type.dart from https://dart-review.googlesource.com/c/sdk/+/228541 which will only arrive in dart:ffi in 2.17 so that we can use this in Dart 2.16.

Adds support for the common C types:

• char
• unsigned char
• signed char
• short
• unsigned short
• int
• unsigned int
• long
• unsigned long
• long long
• unsigned long long
• uintptr_t
• size_t
• wchar_t

Requires Dart 2.16.

Unblocks:

• Support size_t, int, and other common C types // platform independent bindings dart-lang/native#530

[dcharkes]

@mannprerak2 any types you think we should add to this PR?

[mannprerak2]

I think this would suffice.

[mkustermann]

lgtm with comments. Though our offline discussion decided we'll put them into dart:ffi. I suppose you're intending to do both?

[dcharkes]

lgtm with comments. Though our offline discussion decided we'll put them into dart:ffi. I suppose you're intending to do both?

Yes both, so that we can use package:ffi with 2.16 stable and then dart:ffi from 2.17 stable (and then we reexport those in this package).

Let's land the SDK one first, we can do easier C++ tests there. And then copy the definitions over to this PR.

SDK CL: https://dart-review.googlesource.com/c/sdk/+/228541