pgsql: tsearch: use database default collation for parsing.

tsearch: use database default collation for parsing.

Previously, tsearch used the database's CTYPE setting, which only
matches the database default collation if the locale provider is libc.

Note that tsearch types (tsvector and tsquery) are not collatable
types. The locale affects parsing the original text, which is a lossy
process, so a COLLATE clause on the already-parsed value would not
make sense.

Reviewed-by: Peter Eisentraut <peter(at)eisentraut(dot)org>
Discussion: https://postgr.es/m/0151ad01239e2cc7b3139644358cf8f7b9622ff7.camel@j-davis.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/e113f9c102b7e2462facf0ecffc97f8093efed54

Modified Files
--------------
src/backend/tsearch/ts_locale.c | 40 ++++++++--------------
src/backend/tsearch/wparser_def.c | 71 +++++++--------------------------------
2 files changed, 27 insertions(+), 84 deletions(-)