Requiring top-level {} or () for (usually) hand-written files is awkward
and even a little error prone, and certainly ugly at times. With this,
loaders that expect a particular format can specify the format a little
more directly.
I ran into the need to get at the label of labeled array element and the
best way seemed to be by setting the name field of the plfield_t item
passed to the parser function, and then found that PL_ParseSymtab
already does this. I then decided passing the array index would also be
good, and the offset field made sense.
I'm not sure what I was thinking when I made PL_RemoveObjectForKey take
a const plitem. One of those times where C could do with being a little
more strict.
