various coverity-inspired fixes

. some strncpy/strcpy to strlcpy conversions
	. new <minix/param.h> to avoid including other minix headers
	  that have colliding definitions with library and commands code,
	  causing parse warnings
	. removed some dead code / assignments

kernel/kernel.h

@@ -34,6 +34,7 @@
 #include <timers.h>		/* watchdog timer management */
 #include <errno.h>		/* return codes and error numbers */
 #include <sys/param.h>
+#include <minix/param.h>
 
 /* Important kernel header files. */
 #include "config.h"		/* configuration, MUST be first */