PL/Python: Add result object str handler

This is intended so that say plpy.debug(rv) prints something useful for
debugging query execution results.

reviewed by Steve Singer
Perform line wrapping and indenting by default in ruleutils.c.

This patch changes pg_get_viewdef() and allied functions so that
PRETTY_INDENT processing is always enabled.  Per discussion, only the
PRETTY_PAREN processing (that is, stripping of "unnecessary" parentheses)
poses any real forward-compatibility risk, so we may as well make dump
output look as nice as we safely can.

Also, set the default wrap length to zero (i.e, wrap after each SELECT
or FROM list item), since there's no very principled argument for the
former default of 80-column wrapping, and most people seem to agree this
way looks better.

Marko Tiikkaja, reviewed by Jeevan Chalke, further hacking by Tom Lane