debian/rules: correcting install of zarafa.pc for multiarch support

The default installation of /usr/lib/pkgconfig/zarafa.pc doesn't fit
Debians multiarch support. The .pc file has to be installed into
/usr/lib/$DEB_HOST_MULTIARCH/pkconfig/ instead.
debian/rules: change obsolet dh_pysupport to dh_python2

The old helper dh_pysupport shouldn't be longer used, changed the
Build-Depends and the debian/rules files to the new dh_python2 helper.