Change hardcoded ../common paths, which will break when moving the
project specific manuals in other repositories, to ./common so they
use the dynamically created symlink that always points to the right
path.
(moving manuals to project repositories 9/19)
Change-Id: I5368bcff34586c515af23e5a868417e561fd539d
Build project independent "test-usermanual.pdf" (with all common
chapters automatically included) and "test-vty-reference.pdf" files.
This allows testing if changed common chapters and the build scripts
are still working, even when the project specific manuals will be moved
away from this repository.
(moving manuals to project repositories 2/19)
Related: OS#3386
Change-Id: Ia74e32678c95e22ba493e80d0a4a8f783c5a5ddf