Add missing require
Force usage of pipes for subprocess communication

The Emacs Lisp manual documents pipes as more efficient for background
processes.  Since our checkers are exactly that, and don't do user
interaction, let's follow this advice.
Do not attempt to select deleted buffers
Teardown Flycheck when killing the buffer

Kills a running syntax check, and cleans up all temporary buffer copies
before actually killing the buffer.
Be more friendly to the debugger
Add @bbatsov to credits

Thanks for your help, and for adding Flycheck to Prelude, @bbatsov.
Add @steckerhalter to credits

Thanks for your phpcs checker.
Add @dhaley to credits

Thanks for your help in shaping and testing the PHP CodeSniffer checker
Un-break error handling with debugger enabled

We need to handle these errors even with debugger enabled, to make sure
that the UI is properly updated, and necessary cleanup actions are run.

This reverts commit 8b4347423c90d08e983d30dae8a34db29263d5d1.
Do not trigger early cleanup in test.

flycheck-running-p may clean up the process before it is actually
started.  Let's just check that there *is* a process after starting the
syntax check and ignore the actual process state.