utcb handling helper routines for the thread library.

This is one of the steps we need in the process of providing a similar interface
for thread creation which can be found in the mainstream operating systems like
Linux.

conts/libl4thread/src/thread.c

@@ -1,9 +1,10 @@
 /*
  *
  */
-
 #include <stdio.h>
 
+extern void utcb_test(unsigned long utcb_start, unsigned long utcb_end);
+
 void l4thread_print(void)
 {
 	printf("Hello world from libl4thread!\n");