Try to make array_in's behavior a tad less bizarre. Leading whitespace

Try to make array_in's behavior a tad less bizarre.  Leading whitespace
before a data item is now always skipped, rather than only sometimes.
Backslashes not within double-quoted text are treated reasonably, as
are multiple sequences of quoted text in a single data item.  But it
still seems rather prone to misbehavior if the input is not completely
syntactically correct --- in particular, garbage following a right brace
will be ignored.