pgsql: Don't downcase non-ascii identifier chars in multi-byte encoding

Don't downcase non-ascii identifier chars in multi-byte encodings.

Long-standing code has called tolower() on identifier character bytes
with the high bit set. This is clearly an error and produces junk output
when the encoding is multi-byte. This patch therefore restricts this
activity to cases where there is a character with the high bit set AND
the encoding is single-byte.

There have been numerous gripes about this, most recently from Martin
Schäfer.

Backpatch to all live releases.

Branch
------
REL9_2_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/a56c92f938f81df6b9d59b5bb7edc44008f0e06c

Modified Files
--------------
src/backend/parser/scansup.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)