update upstream

See merge request !2

It seems that the distributions places nologin in different
places (e.g. deb based distribution in /usr/sbin, rpm based and gentoo
in /sbin).  This patch fixes this behaviour searching for nologin in
the PATH environment variable.

Now a variable for the SPOOL_DIR is been allocated.

Now a variable is used for the spool file and the installation process
is less verbose.

As for the PostInstall script, the Uninstall script must be
adapted to the new username (_cado)

The getopt_long descriptors was not correctly terminated.
To avoid a segmentation fault the list should be terminated
by an array composed of 4 NULLs.

PostInstall was refactored to mimick the debian installer.

update upstream

See merge request !1

PostInstall check, removed unused retvalue warnings, config.h patch

CMake conversion

cadrop permits to drop ambient capabilities.

With this fix /proc/<pid>/cmdline is preserved.

users cannot use symlinks when editing the scado file.