Capability checking added as compiling code.

Capability checking for thread_control, exregs, mutex, cap_control,
ipc, and map system calls.

The visualised model is implemented in code that compiles, but
actual functionality hasn't been tested.

Need to add:
- Dynamic assignment of initial resources matching with what's
defined in the configuration.
- A paged-thread-group, since that would be a logical group of
seperation from a capability point-of-view.
- Resource ids for various tasks. E.g.
  - Memory capabilities don't have target resources.
  - Thread capability assumes current container for THREAD_CREATE.
  - Mutex syscall assumes current thread (this one may not need
    any changing)
  - cap_control syscall assumes current thread. It may happen to
    be that another thread's capability list is manipulated.

Last but not least:
- A simple and easy-to-use userspace library for dynamic expansion
  of resource domains as new resources are created such as threads.

include/l4/api/capability.h

@@ -10,6 +10,8 @@
 #define CAP_CONTROL_NCAPS		0x00
 #define CAP_CONTROL_READ		0x01
 #define CAP_CONTROL_SHARE		0x02
+#define CAP_CONTROL_GRANT		0x03
+#define CAP_CONTROL_MODIFY		0x05
 
 #define CAP_SHARE_MASK			0x1F
 #define CAP_SHARE_SPACE			0x01