improve line-breaking and indentation of foreign options dump

Currently, pg_dump dumps foreign options in a single line, for example

CREATE SERVER cluster FOREIGN DATA WRAPPER plproxy OPTIONS (p0 'host=host0', p1 'host=host1', p2 'host=host2', p3 'host=host3');

I think it would be nicer if it looked more like this:

CREATE SERVER cluster FOREIGN DATA WRAPPER plproxy OPTIONS (
p0 'host=host0',
p1 'host=host1',
p2 'host=host2',
p3 'host=host3'
);

Attached is a patch to implement that, and a test file to play around
with.