quotes in SET grammar

Christopher's patch to fix docs regarding single- and double-quotes in
SET syntax got me looking at gram.y. It turns out that although we allow
lists of double-quoted strings in SET, we do not allow lists of
single-quoted strings (the latter should have been preferred afaik). And
although we allow single-quoted strings in SET TIME ZONE, we do not
allow double-quoted strings! So things seem inconsistant to me.

Possible cases look like

SET TIME ZONE 'pst8pdt';
SET TIME ZONE "pst8pdt";
SET DATESTYLE = "US","ISO";

Is there any objection to allowing both single- and double-quoted
strings in SET? Or should I remove the double-quoted variety altogether?
I've got patches for the former, but am willing to consider either
solution. afaik single-quoted strings would be sufficient to cover
users' expectations, and all cases are extentions to SQL9x syntax, which
only specifies SET TIME ZONE with a numeric offset. Comments?

- Thomas