BUG #9227: Error on SELECT ROW OVERLAPS ROW with single ROW argument

The following bug has been logged on the website:

Bug reference:      9227
Logged by:          Joshua Yanovski
Email address:      pythonesque@gmail.com
PostgreSQL version: 9.3.2
Operating system:   Ubuntu 12.0.4
Description:

# SELECT ROW (1) OVERLAPS ROW (2);
ERROR:  XX000: unrecognized node type: 656
LOCATION:  transformExprRecurse, parse_expr.c:359

I'm not sure why this even parses, as it's not documented to do so.  I do
notice, however, that in makeOverlaps in gram.y creates a recursive list
when largs or args has only one argument, which seems wrong to me.