Add journal.c to the jbd2 Makefile and update includes to use the
ext4l compatibility layer.
Add stubs for functions from recovery.c, revoke.c, and transaction.c
that journal.c depends on.
Remove JBD2 function stubs from stub.c that are now provided by
journal.c.
Co-developed-by: Claude Opus 4.5 <noreply@anthropic.com>