This adds some feedback to a keypress which previously had no visible effect.

While the text “no input” isn’t the most descriptive, it was the only one I
could think of which fit into the unlock indicator circle. If you have a better
suggestion, let me know.

fixes #164

Also apply two security measures for OpenBSD:
- use explicit_bzero(3)
- mlock(2) works for non-root users too

there is nothing PAM-specific about pam_state or pam_state_t. therefore
rename them to be authenticator independant.

To give a feedback for when the pointer couldn't be grabbed,
displaying an error message before exiting.

Display "locking…" message when grabbing the pointer/keyboard,
after at least 250 ms of unfruitful attempts. If grabbing
eventually fails, application will not fork and return 1.

From here on, we’ll use clang-format to automatically format the source.

This has worked well in i3, so we are introducing it for i3lock.

See also:
http://article.gmane.org/gmane.linux.kernel/1268792

The C compiler will handle (void) as "no arguments" and () as "variadic
function" (equivalent to (...)) which might lead to subtle errors, such
as the one which was fixed with commit 0ea64ae4.