Several documentation updates for the pending 1.2 release:

* More mentions of new --only-indexes feature
 * Note we now support up to Postgres 9.3, and get rid of outdated list
   of supported operating systems. (As far as we know, pg_repack should
   build on any platforms supported by PostgreSQL itself, although no one
   has tested the Windows build in a long time.)
 * Remove most of the warnings about data corruption possible with concurrent
   DDL: this should no longer be a concern now that we hold an ACCESS SHARE
   lock during full-table repacks. Keep a short warning about old versions
   being susceptible to this problem, just to make clear that it's fixed now
   and as an enticement to upgrade.
 * A few grammar, phrasing, and typo fixes

regress/expected/repack.out

@@ -340,7 +340,7 @@ CREATE TABLE trg2 (id integer PRIMARY KEY);
 CREATE TRIGGER z_repack_trigger BEFORE UPDATE ON trg2 FOR EACH ROW EXECUTE PROCEDURE trgtest();
 \! pg_repack --dbname=contrib_regression --table=trg2
 INFO: repacking table "trg2"
-WARNING: the table "trg2" has already a trigger called "z_repack_trigger"
+WARNING: the table "trg2" already has a trigger called "z_repack_trigger"
 DETAIL: The trigger was probably installed during a previous attempt to run pg_repack on the table which was interrupted and for some reason failed to clean up the temporary objects.  Please drop the trigger or drop and recreate the pg_repack extension altogether to remove all the temporary objects left over.
 CREATE TABLE trg3 (id integer PRIMARY KEY);
 CREATE TRIGGER z_repack_trigges BEFORE UPDATE ON trg3 FOR EACH ROW EXECUTE PROCEDURE trgtest();