Get size from controlling terminal?

[swsnr]

Currently term_size queries the standard streams to get the terminal size which fails if all are redirected.

However POSIX also provides means to directly get hold of the underlying terminal even if all streams are redirected, via ctermid. This function returns the path to the terminal device which we can then open() to get a file description for ioctl. While man 3 ctermid warns that open may fail, practically it never does, whereas redirection is somewhat common.

Would you mind to add a function which gets the terminal size from the controlling terminal?

[CreepySkeleton]

Sounds good to me, but the future of this crate is somewhat cloudy.