[FIX] account: restore cross-account reconciliation check, disabled by mistake in v6.1

Both the FY closing change and the removal of the
check occurred in v6.1 at revision 6529
revid:qdp-launchpad@openerp.com-20120209170333-8xu7r21hencjwu73.

Also removed code specific to fiscal year closing
in the regular reconciliation operation, as the
FY closing is now using a dedication reconciliation
algorithm.

This is a forward-port of the corresponding patch in v6.1,
at revno 7295 rev-id: odo@openerp.com-20140110154023-12rqfeuwx5fqpdau.