Include <signal.h> instead of depending on namespace pollution in

<sys/param.h>.  Include <sys/types.h> instead of of <sys/param.h>
so that further such dependencies don't develop.

bin/cp/cp.c

@@ -63,13 +63,14 @@ __FBSDID("$FreeBSD$");
  * in "to") to form the final target path.
  */
 
-#include <sys/param.h>
+#include <sys/types.h>
 #include <sys/stat.h>
 
 #include <err.h>
 #include <errno.h>
 #include <fts.h>
 #include <limits.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>