[xmlsec] build config change for nss

[John Belmonte]

Hi,

For the Debian package I've had to change the pkg-config mozilla calls
to xulrunner.  The word is that the Mozilla libraries will no longer be
maintained and everything has been moved to the xulrunner package.

Here is a sed line to make the change:

    sed -i -e 's/mozilla-\(nspr\|nss\)/xulrunner-\1/g' \
        configure.in configure xmlsec-nss.pc.in

--John