Added new signal types for kernel events:

- SIGKMESS: new kernel message (sent to TTY, IS, or LOG)
- SIGKSTOP: MINIX is shut down (sent to TTY-> switch to primary console)
- SIGKSIG: kernel signals pending (sent to PM)

Renamed SYS_SETPRIORITY to SYS_NICE.

lib/syslib/sys_nice.c

@@ -0,0 +1,13 @@
+#include "syslib.h"
+
+/*===========================================================================*
+ *                                sys_nice			     	     *
+ *===========================================================================*/
+PUBLIC int sys_nice(int proc, int prio)
+{
+  message m;
+
+  m.m1_i1 = proc;
+  m.m1_i2 = prio;
+  return(_taskcall(SYSTASK, SYS_NICE, &m));
+}