script-fu used to query the information of every PDB procedure on
startup, in order to get the number of parameters for each
procedure.  This was done so that nullary procedures were defined
in such a way as to accept (and ignore) any number of arguments
(and at least one of the scripts we ship relies on this behavior).
However, this requires expensive back-and-forth communication with
the main GIMP process, which notable slowed down script-fu's
startup, and had a non-negligible impact on GIMP's startup time.

Instead, avoid querying procedure information, and implement the
special behavior for nullary procedures at call time.  We do this
by defining, in addition to the "strict" gimp-proc-db-call
procedure, a "permissive" -gimp-proc-db-call internal procedure,
and using the latter to call the predefined PDB procedures.