Extend the capabilities of is_os to detect more platforms such as
freebsd and openbsd. Also remove `iswin()` helper function as it can be
replaced by `is_os("win")`.
This is essentially a convenience wrapper around the `pending()`
function, similar to `skip_fragile()` but more general-purpose.
Also remove `pending_win32` function as it can be replaced by
`skip(iswin())`.
It is otherwise impossible to determine which test failed sanitizer/valgrind
check. test/functional/helpers.lua module return was changed so that tests which
do not provide after_each function to get new check will automatically fail.
- Modify tty-test to allow easier control over the terminal
- Add a new directory with various terminal tests/specifications
- Remove a pending job/pty test.
- Flush stdout in Screen:snapshot_util() (avoid waiting for the test to finish)
- Replace libuv sigwinch watcher by a sigaction handler. libuv randomly fails to
deliver signals on OSX. Might be related to the problem fixed by
@bbcddc55ee1e5605657592644be0102ed3a5f104 (under the hoods, libuv uses a pipe
to deliver signals to the main thread, which might be blocking in some
situations)
