Convert the project to use the GNU Build System (aka Autotools)

LICENSE was renamed COPYING because otherwise `autoreconf` complains loudly.
This is also the reason AUTHORS, INSTALL, and README were created.

Man pages were moved into src/pam_panic/man and src/pam_panic_pw/man.

Finally, certain variables are passed through the config.h file to the
module rather than as -D flags on the command-line.

src/pam_panic/pam_panic_reject.c

@@ -10,6 +10,7 @@ LICENSE :      GNU-GPLv3
 #include <unistd.h>
 #include <security/pam_ext.h>
 #include <sys/wait.h>
+#include "config.h"
 #include "pam_panic_reject.h"
 
 int reject(char *serious_dev, int8_t bSerious, int8_t bReboot, int8_t bPoweroff){