JOEL4: added l4.c

Added another source file to hold the implementation of helper functions as
part of L4. These are generic, and not system calls.

Signed-off-by: Joel Nider <joel@nider.org>
JOEL4: handle invalid syscall better

When an invalid syscall index is used, pass it as a parameter to the
handling function for easier debugging.

Signed-off-by: Joel Nider <joel@nider.org>
JOEL4: updated KIP information

Added definitions related to KIP information such as kernel version, and L4
API version. Added a helper function to check the KIP magic number.

Signed-off-by: Joel Nider <joel@nider.org>