Doc: fix examples of # operators so they actually work.

These worked as-is until around 7.0, but fail in newer versions because
there are more operators named "#".  Besides it's a bit inconsistent that
only two of the examples on this page lack type names on their constants.

Report: <20160923081530.1517.75670@wrigleys.postgresql.org>

doc/src/sgml/func.sgml

@@ -7594,12 +7594,12 @@ CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple
        <row>
         <entry> <literal>#</literal> </entry>
         <entry>Point or box of intersection</entry>
-        <entry><literal>'((1,-1),(-1,1))' # '((1,1),(-1,-1))'</literal></entry>
+        <entry><literal>box '((1,-1),(-1,1))' # box '((1,1),(-2,-2))'</literal></entry>
        </row>
        <row>
         <entry> <literal>#</literal> </entry>
         <entry>Number of points in path or polygon</entry>
-        <entry><literal># '((1,0),(0,1),(-1,0))'</literal></entry>
+        <entry><literal># path '((1,0),(0,1),(-1,0))'</literal></entry>
        </row>
        <row>
         <entry> <literal>@-@</literal> </entry>