Fix the build by including <sys/param.h> in <sys/clist.h>.

Of course I was silly enough to only check LINT for build failures, but not
the userspace bits. In the mpsafetty branch I didn't notice this, because
<sys/clist.h> never got included in userspace.

Approved by:	philip (mentor)
Pointy hat to:	me :-(

sys/sys/clist.h

@@ -33,6 +33,8 @@
 #ifndef _SYS_CLIST_H_
 #define _SYS_CLIST_H_
 
+#include <sys/param.h>
+
 /*
  * Clists are character lists, which is a variable length linked list
  * of cblocks, with a count of the number of characters in the list.