Implemented a protocol between client and pager for requesting caps.

In posix, test0 makes inter-space ipc for testing extended ipc. This
correctly fails when only the cap to ipc to pager is given to all tasks
in the container.

In order to overcome this problem, the tasks who fork for doing ipc to
each other make a request to the pager to get capabilities to do so.

Pager finds its own widened ipc capability over the container, replicates
it, validates and reduces it to desired boundaries (i.e. just ipc betw.
two spaces) and grants it as IMMUTABLE to requesting tasks.

This protocol may be useful in implementing a client/server capability
request relationship. Code builds but untested.

include/l4/generic/capability.h

@@ -59,8 +59,8 @@ struct capability {
 
 	/* Capability identifiers */
 	l4id_t capid;		/* Unique capability ID */
-	l4id_t resid;		/* Targeted resource ID */
 	l4id_t owner;		/* Capability owner ID */
+	l4id_t resid;		/* Targeted resource ID */
 	unsigned int type;	/* Capability and target resource type */
 
 	/* Capability limits/permissions */