Fix for Bug 6531 - clicking print button in opac causes 404 error

Fix for Bug 6531 - clicking print button in opac causes 404 error

opac-detail and opac-ISBDdetail both use window.print(), so I've
added that to opac-MARCdetail as well. I've also eliminated the
"javascript:" pseudo-protocol because it's pointless. I'd
prefer to have a real link for non-js users but that will have
to wait for another bug.

After applying this patch users with JS enabled should get a
print prompt after clicking the "Print" link on opac-MARCdetail.pl

Signed-off-by: Magnus Enger <magnus@enger.priv.no>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>