Overhaul build system and add support for disabling inetd support.

This patch adds support for a configure script and with it
support for disabling inetd support.  See the output from

    ./configure --help

* Add configure script
* Sprinkle #ifdef fairy dust on svc.c when inetd support is disabled
* Use GCC built-in autodep calculator (-MMD -MP)
* Fix name space issue with include files, use relative paths
* Disable username/group name to uid/gid functions in static builds
* Bug out (error) if a user tries to build the bootmisc plugin static

Possibly fixes GitHub issue #5 and issue #6.

NOTE: The static build has not received any testing at all!

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

plugins/time.c

@@ -26,7 +26,7 @@
 #include <unistd.h>		/* STDIN_FILENO */
 #include <sys/socket.h>
 
-#include "plugin.h"
+#include "../plugin.h"
 
 /* UNIX epoch starts midnight, 1st Jan, 1970 */
 #define EPOCH_OFFSET 2208988800ULL