pgsql: pg_trgm's set_limit() now uses SetConfigOption()

pg_trgm's set_limit() now uses SetConfigOption()

Deprecated set_limit() is modified to use SetConfigOption() to set
similarity_threshold which is actually an instance of
pg_trgm.similarity_threshold GUC variable. Previous coding directly sets
similarity_threshold what could cause an inconsistency between states of
actual variable and GUC representation.

Per gripe from Tom Lane

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/aa698d753566f68bdd54881d30b1a515b0327b0e

Modified Files
--------------
contrib/pg_trgm/trgm_op.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)