date/time formats in 7.2

For 7.2, to support some ISO-8601 variants, I'm tightening up the date
delimiter parsing to require the same delimiter to be used between all
parts of a date.

Does anyone use the German date notation for PostgreSQL? If so, what is
the actual format you input? The reasons I'm asking are:

o I had recalled that the format was "dd.mm/yyyy", but actually
PostgreSQL emits "dd.mm.yyyy".

o By tightening up the parsing, "dd.mm.yyyy" would be accepted, but
"dd.mm/yyyy", "yyyy.mm-dd", etc would not.

o The stricter parsing in this area would allow more general parsing
elsewhere, enabling other variants such as

yyyymmddThhmmss
yyyymmdd hhmmss.ss-zz
Thhmmss-zz

With these changes, more formats should be correctly handled, including
some edge cases which should have worked but seemed not to; the current
regression tests still all pass. As an example of edge case troubles,
7.1 accepts both of the following:

timestamp '2001-12-27 04:05:06-08'
timestamp '2001-12-27 040506 -08'

But rejects the latter if the space before the time zone is removed:

timestamp '2001-12-27 040506-08'

Comments? Suggestions?

- Thomas