Preparing to add utcbs at disjoint virtual addresses.

This will help when syscalls have long arguments individual
utcbs can be mapped to server tasks and kept mapped in until the
tasks die, as opposed to map requests every time a server task maps
a different utcb at the same virtual address.

The changes have preparation code to also passing the utcb info
through the stack as part of the environment.

To sum up env and arg regions have also been added above the stack and
env region is to be used to pass on the utcb address information at
task startup.

tasks/libl4/src/init.c

@@ -20,6 +20,9 @@ __l4_kmem_reclaim_t __l4_kmem_reclaim = 0;
 
 struct kip *kip;
 
+/* UTCB address of this task. */
+struct utcb *utcb;
+
 void __l4_init(void)
 {
     kip = l4_kernel_interface(0, 0, 0);