termios2 shouldn't exist on musl targets

[Susurrus]

musl doesn't include the termios2 API, but those structs are declared by libc. They should be removed.

[gnzlbg]

I think we can go ahead and do this breaking change, care to submit a PR ?

[Susurrus]

I already have a PR in #629, however it contains other breaking changes to datatypes around termios. Do you want me to break it out as a separate PR or is that whole PR on the table for merging?

[gnzlbg]

Separate PR would be better (EDIT: #629 has been merged).

[Susurrus]

I think this can be closed now that #629 was merged.