Add notice about unsupported C-like escapes in PG SQL (merge from develbranch_6)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@34298 15284696-431f-4ddb-bdfa-cd5b030d7da7

db/drivers/postgres/grass-pg.html

@@ -35,6 +35,8 @@ db.tables -p
 
 All SQL commands supported by PostgreSQL.
 
+It's not possible to use C-like escapes (with backslash
+like \n etc) within SQL syntax. 
 
 <H2>Operators available in conditions</H2>