Fix a hang on Unix

Fancy shutdown, fancy problems, let's hope this release has no races.

With this release, if you open a (log?) file in moar, and more lines are added to the file after you start moar, moar will pick up the new lines and display them.

Also, if you have a terminal editor (nano, vim etc), and press "v" to edit a file, moar will now not steal the first byte from your editor any more. Improved on Unix, Windows unchanged, PRs welcome.

Actually tested on Windows, shutdown works again.

Last known good release on Windows was v1.23.15.

Before this release, pressing v to edit a file on Windows would tell you your editor was not executable.

With this release, executability detection on Windows should now work.

By pressing v.

Before this change, v only worked for actual files.

With this change in place, v will also work for piped input.

Piped input will be written into a temporary file, then the editor will be opened with that file.

Before this release, if you pressed v to open the current file in your $EDITOR, and the editor was terminal based (think nano, vim), then the editor was really laggy.

That lagginess has been fixed in this release.

With this release, if you press v while viewing a file, moar will launch an editor to edit the file. The editor is determined by the $VISUAL and $EDITOR environment variables.

Fixes #211.

Before this release, searching was single threaded.

With this release, searching now uses all available cores, which makes searching large files a lot faster.

Searching a nine hundred thousand lines file now works fine on my laptop, which it did not before.