Remove --with-plugindir=DIR, use --prefix or --libdir instead

The /lib/finit/plugins path is as of this patch not longer possible to
change.  Use --prefix or --libdir instead to change the leading path.

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

src/plugin.h

@@ -24,6 +24,7 @@
 #ifndef FINIT_PLUGIN_H_
 #define FINIT_PLUGIN_H_
 
+#include <config.h>
 #include <uev/uev.h>
 #include <lite/queue.h>		/* BSD sys/queue.h API */