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/bootmisc.c

@@ -24,9 +24,13 @@
 #include <string.h>
 #include <utmp.h>
 
-#include "finit.h"
-#include "helpers.h"
-#include "plugin.h"
+#include "../finit.h"
+#include "../helpers.h"
+#include "../plugin.h"
+
+#ifdef ENABLE_STATIC
+#error This plugin uses getuser(), which relies on dynamically linked GLIBC.  Cannot be built statically!
+#endif
 
 /*
  * Setup standard FHS 2.3 structure in /var, and