This serves to provide a quick way to prevent the screen lock from
starting when accidentally launched (e.g. while watching a video).

The amount of time is controlled by the environment variable
XSECURELOCK_ALLOW_UNAUTHENTICATED_WAKEUP_TIME_SEC and can be set in the
range from 0 (feature turned off) to 10 (maximum allowed value).

During this time, the screen saver does not run and an animation
indicating this process is drawn instead.

Requires -lrt and CLOCK_MONOTONIC.

Fixes #12.

auth_pam_x11: support font selection

Usage:

- Find a good font name with xfontsel.
- Launch the screen saver via something like:

```
XSECURELOCK_FONT=-misc-fixed-medium-r-normal--20-200-75-75-c-100-iso10646-1 xsecurelock 
```

If the font can for some reason not be loaded, we're still falling back to fixed to allow SOME unlocking.

Many other screen savers send the wake-up keypress to the auth dialog,
so let's offer this feature to. Do read the security notes about this in
the source, though.

Fixes #14.

We have no need of handling this, however we don't want to spam about
this event on stderr.

Should fix some issues with semi-transparent notification windows.

It's sad that this is required, but some XScreenSaver hacks cause
XSecureLock to lose the grab on MotionNotify.

These can be overridden via:
- ./configure --with-default-auth-module=... --with-default-saver-module=...
- $XSECURELOCK_AUTH and $XSECURELOCK_SAVER environment variables
- Command line arguments (which work exactly as before)

Previously, the xset command sometimes got killed in response to
ScreenSaverNotify.

Instead, raise on VisibilityNotify. This makes sure possible email
notifications or other stuff show up as shortly as possible.

Quotes are required there...

Also, some minor changes done while auditing during documenting,
including fixes for:

- A file descriptor leak in the auth child (may DoS the screen).
- A race condition between querying display size and creating the
  window.

The saver itself then will use a subwindow of the grab_window. End
result: in case the saver calls XUngrabKeyboard on the window it's told,
it no longer will stop our grab. The "bumps" XScreenSaver hack does
exactly this.

With this, I also could remove the previously existing hack to reinstate
the grab every 100ms.

This makes the behavior of pressing a key while the saver is running
more intuitive.

Sorry for that. After this, unlocking properly authenticates again.

Use this if you for some reason can't use PAM.

This will ask for a new password if the user's password has expired
before unlocking.

As with XScreenSaver, checking for its return value needs to be
explicitly enabled via --enable-pam-check-account-type.

A random byte in memory was set to 0 in auth_pam_x11, and the password
possibly not zero terminated.

Thanks, Coverity!

Usage: --with-pam-service-name=xscreensaver.