* Improve compatibility with OpenBSD

* Fix indefinite blocking

This reverts commit 1e859eb137.
We will use atool on OS X as well, it can be brewed easily.

...because you need to know where you are.

* Prevent nnn from waiting on open file process

* Add env var flag to not wait for child process when opening file

* Set nowait flag once to skip bit-or every time we open a file

* Add documentation for NNN_NOWAIT

Fix regression from 1e5a0b8c5b.