fixes #184

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

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.

fixes #51

The script used to make these changes can be found at:

   https://gist.github.com/Deiz/32322020f76d23e2bf8f

When the unlock indicator warns the user that a password was typed
wrong, it now also reports the state of the capslock and numlock
modifiers.

Signed-off-by: Alexandre Boeglin <alex@boeglin.org>

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.

This closes #1243

Thanks to Ran Benita and Daniel Stone (the libxkbcommon authors) for
answering my questions and reviewing this code.

With this commit, input handling should be more correct with using less
code (in i3lock, that is).

Fixes: #712

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.

Needed to compile without libcairo.