After the few specific args (drawable/filter ID, opacity, blend mode, op
name…), the op argument names can be passed either as string or with the
new argument name syntax. The error message though focus on argument
name type.
Also fix the argument count for the various possible cases (when
configuring with (gimp-drawable-filter-configure) or
(gimp-drawable-merge|append-new-filter), the start arg count is
different).
f17a42be75