Problem:
jobwait() returns early if the job was stopped, but the job might have
pending callbacks on its event queue which are required to complete its
teardown. State such as term->closed might not be updated yet (by the
pending callbacks), so codepaths such as :bdelete think the job is still
running.

Solution:
Always flush the job's event queue before returning from jobwait().

ref #15349

- If the terminal job is still running then ! is still required.

Closes #4683

In Lua patterns the hyphen works like a non-greedy version of Vim's `*`.
- Use `%-` when you need a literal hyphen.
- If you don't need a regular expression at all, use something like
  ```
  string.find(text, pattern, 1, true)
  ```
  so that the pattern is regarded as a plain, non-magical string.
  See [1] and [2] in the Lua manual.

[1]: https://www.lua.org/manual/5.1/manual.html#pdf-Patterns
[2]: https://www.lua.org/manual/5.1/manual.html#pdf-string.find

User config may set $PS1 for a colored prompt.
It breaks the screen tests.

Problem:    Using :wqa exits even if a job runs in a terminal window. (Jason
            Felice)
Solution:   Check if a terminal has a running job. (closes vim/vim#2654)
https://github.com/vim/vim/commit/7a76092a51fc5446426a4bfd9eb6503ec61bf9e9