Added handle_t type to server interface so that we can make handles
pointers later on.
Always use 0 to signal invalid handle in server requests.

diff --git a/server/process.h b/server/process.h
index 204fd04..f20d185 100644
--- a/server/process.h
+++ b/server/process.h
@@ -74,7 +74,7 @@
 
 extern struct thread *create_process( int fd );
 extern struct process *get_process_from_id( void *id );
-extern struct process *get_process_from_handle( int handle, unsigned int access );
+extern struct process *get_process_from_handle( handle_t handle, unsigned int access );
 extern int process_set_debugger( struct process *process, struct thread *thread );
 extern void add_process_thread( struct process *process,
                                 struct thread *thread );