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.

configure.ac

@@ -0,0 +1,48 @@
+AC_INIT([pam_panic], [0.1.0], [], [pam_panic])
+AC_CONFIG_AUX_DIR([build-aux])
+AM_INIT_AUTOMAKE([-Wall])
+AC_PREREQ([2.69])
+AC_CONFIG_MACRO_DIR([m4])
+AC_CANONICAL_HOST
+
+AC_SUBST(PACKAGE)
+AC_SUBST(VERSION)
+
+AC_USE_SYSTEM_EXTENSIONS
+AC_PROG_CC
+AM_PROG_AR
+
+AC_PATH_PROG([REBOOT], [reboot])
+AC_SUBST(REBOOT)
+AC_PATH_PROG([POWEROFF], [poweroff])
+AC_SUBST(POWEROFF)
+AC_PATH_PROG([CRYPTSETUP], [cryptsetup])
+AC_SUBST(CRYPTSETUP)
+
+AC_ARG_ENABLE(securedir,
+    AS_HELP_STRING([--enable-securedir=DIR],
+        [path to location of PAMs @<:@default=$libdir/security@:>@]),
+    SECUREDIR=$enableval, SECUREDIR=$libdir/security)
+AC_SUBST(SECUREDIR)
+
+AC_ARG_ENABLE(ppassfile,
+    AS_HELP_STRING([--enable-ppassfile=FILE],
+        [path to file to be used for storing passwords @<:@default=$sysconfdir/pam_panic/auth@:>@]),
+    PPASSFILE=$enableval, PPASSFILE=$sysconfdir/pam_panic/auth)
+AC_SUBST(PPASSFILE)
+
+LT_INIT([disable-static])
+AC_ENABLE_STATIC([no])
+AC_ENABLE_SHARED([yes])
+
+AC_CONFIG_FILES([
+    Makefile
+    src/pam_panic/config.h
+    src/pam_panic/Makefile
+    src/pam_panic/man/Makefile
+    src/pam_panic_pw/config.h
+    src/pam_panic_pw/Makefile
+    src/pam_panic_pw/man/Makefile
+])
+
+AC_OUTPUT