manpages: VFS Compat API manpage update.

- Reflect a bit better what's on the current codebase with
  regards to the old VFS API, which is still in use for many
  filesystems.
- Pseudocode present on the old API manpages has been removed.

In-discussion with: swildner
manpages: Add an updated version of vn_lock.9
manpages: Forgot to hook vn_lock.9 into the build.
man9: Fix Makefile sorting.