System task initialization moved to main()

- the system task initialization code does not really need to be part
  of the system task process. An earlier initialization in kernel is
  cleaner as it does not only initialize the syscalls but also irq
  hooks etc.

kernel/proto.h

@@ -59,6 +59,7 @@ _PROTOTYPE( void send_sig, (int proc_nr, int sig_nr)			);
 _PROTOTYPE( void cause_sig, (proc_nr_t proc_nr, int sig_nr)			);
 _PROTOTYPE( void sig_delay_done, (struct proc *rp)			);
 _PROTOTYPE( void sys_task, (void)					);
+_PROTOTYPE( void system_init, (void)					);
 #define numap_local(proc_nr, vir_addr, bytes) \
 	umap_local(proc_addr(proc_nr), D, (vir_addr), (bytes))
 _PROTOTYPE( phys_bytes umap_grant, (struct proc *, cp_grant_id_t, vir_bytes));