Rename findlib package from 'libvhd' to 'vhdlib', to workaround linking ...

...problems

Unfortunately 'libvhd' was leading to linking failures, probably due
to the naming of some intermediate archives. Renaming to 'vhdlib' fixes
the problem without reintroducing the old name ('libxcplib')

Signed-off-by: David Scott <dave.scott@eu.citrix.com>