[Users] McLachlan boundary conditions

Hi,

Three months ago, I corrected a bug in the McLachlan boundary conditions. See https://trac.einsteintoolkit.org/ticket/848 for more details. All bug fixes tend to be discussed on trac.einsteintoolkit.org, but we should probably announce bugs like this which people might miss otherwise on the mailing list as well. Someone has just found that an unexplained numerical blowup was fixed by applying the above patch. The bug affects the Maxwell release, but is fixed in Lovelace. Anyone still using Maxwell and McLachlan radiative boundary conditions with conformalMethod = 1 should probably apply that fix or update to Lovelace. Similarly, ML_ADMConstraints is incorrect in Maxwell, and fixed in Lovelace.