Implement two types of suid/sgid support for BusyBox:

1) tinylogin like with compile time selection and a chown root.root
2) Runtime configurable via /etc/busybox.conf (docu is in the works)
[Parts of this patch may overlap with my other two patches]

include/libbb.h

@@ -37,6 +37,8 @@
 
 #include <features.h>
 
+#include "config.h"
+
 #if (__GNU_LIBRARY__ < 5) && (!defined __dietlibc__)
 /* libc5 doesn't define socklen_t */
 typedef unsigned int socklen_t;