Add -a switch to cause H atoms to be added, deleting existing ones.
With -a, mengine behaves as the original.
Formal charges are not always preserved, by the original or
the modified mengine with or without the -a switch.
It appears that negative charges are preserved (benzoic acid).
A positive charge on a N atom (an amine) is not preserved.
Charges are recognized in CHG records and in atom records.
Charges are output only in atom records.