gen_node_support.pl: Mark location fields as type alias ParseLoc
Instead of the rather ugly type=int + name ~= location$, we now have a
marker type for offset pointers or sizes that are only relevant when a
query text is included, which decreases the complexity required in
gen_node_support.pl for handling these values.
Author: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAEze2WgrCiR3JZmWyB0YTc8HV7ewRdx13j0CqD6mVkYAW+SFGQ@mail.gmail.com