Ongoing work for adding per-thread UTCB structures.

Added setting of utcb address to l4_thread_control.
This is going to be moved to exchange_registers() since we need to pass
both the utcb physical and virtual address and exregs fits such context
modification better than thread_control.

tasks/libl4/include/l4lib/init.h

@@ -0,0 +1,6 @@
+#ifndef __L4LIB_INIT__
+#define __L4LIB_INIT__
+
+void __l4_init(void);
+
+#endif