Clean up half a dozen of header files that are no longer needed now that

we use struct sppp_parms instead of struct sppp for userland programs.

MFC after:	1 month

sbin/spppcontrol/spppcontrol.c

@@ -29,18 +29,11 @@ static const char rcsid[] =
   "$FreeBSD$";
 #endif /* not lint */
 
-#include <sys/param.h>
-#include <sys/callout.h>
+#include <sys/types.h>
 #include <sys/ioctl.h>
-#include <sys/mbuf.h>
 #include <sys/socket.h>
 
 #include <net/if.h>
-#include <net/if_var.h>
-#include <netinet/in.h>
-#include <netinet/in_systm.h>
-#include <netinet/ip.h>
-#include <net/slcompress.h>
 #include <net/if_sppp.h>
 
 #include <err.h>