Kernel: clean up include statements a bit

Coverity was flagging a recursive include between kernel.h and
cpulocals.h. As cpulocals.h also included proc.h, we can move that
include statement into kernel.h, and clean up the source files'
include statements accordingly.

kernel/table.c

@@ -30,8 +30,6 @@
 #define _TABLE
 
 #include "kernel.h"
-#include "proc.h"
-#include "ipc.h"
 #include <minix/com.h>
 
 /* The system image table lists all programs that are part of the boot image.