commpage: randomize position of commpage

This patch introduces randomization of commpage position. From now on commpage
table contains offsets from begining to of the commpage to the particular
commpage entry. Similary addresses of symbols in ELF memory image "commpage"
are just offsets from the begining of the commpage.

This patch also updates KDL so that commpage entries are recognized and shown
correctly in stack trace. An update of Debugger is yet to be done.

headers/private/runtime_loader/runtime_loader.h

@@ -51,6 +51,7 @@ struct rld_export {
 	void (*call_termination_hooks)();
 
 	const struct user_space_program_args *program_args;
+	const void* commpage_address;
 };
 
 extern struct rld_export *__gRuntimeLoader;