udhcp: fix indentation and style.

Eliminate (group) a lot of smallish *.h files
Remove lots of unneeded #includes

networking/udhcp/signalpipe.c

@@ -20,17 +20,9 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
-#include <unistd.h>
-#include <fcntl.h>
-#include <signal.h>
-#include <sys/types.h>
-#include <sys/socket.h>
-#include <sys/select.h>
-
-
-#include "signalpipe.h"
 #include "common.h"
 
+
 static int signal_pipe[2];
 
 static void signal_handler(int sig)