Mark some contrib modules as "trusted".

Mark some contrib modules as "trusted".

This allows these modules to be installed into a database without
superuser privileges (assuming that the DBA or sysadmin has installed
the module's files in the expected place).  You only need CREATE
privilege on the current database, which by default would be
available to the database owner.

The following modules are marked trusted:

btree_gin
btree_gist
citext
cube
dict_int
earthdistance
fuzzystrmatch
hstore
hstore_plperl
intarray
isn
jsonb_plperl
lo
ltree
pg_trgm
pgcrypto
seg
tablefunc
tcn
tsm_system_rows
tsm_system_time
unaccent
uuid-ossp

In the future we might mark some more modules trusted, but there
seems to be no debate about these, and on the whole it seems wise
to be conservative with use of this feature to start out with.

Discussion: https://postgr.es/m/32315.1580326876@sss.pgh.pa.us