pgsql: Improve error message annotation for GRANT/REVOKE on untrusted P

Improve error message annotation for GRANT/REVOKE on untrusted PLs.

The annotation for "ERROR: language "foo" is not trusted" used to say
"HINT: Only superusers can use untrusted languages", which was fairly
poorly thought out. For one thing, it's not a hint about what to do,
but a statement of fact, which makes it errdetail. But also, this
fails to clarify things much, because there's a missing step in the
chain of reasoning. I think it's more useful to say "GRANT and REVOKE
are not allowed on untrusted languages, because only superusers can use
untrusted languages".

It's been like this for a long time, but given the lack of previous
complaints, I don't think this is worth back-patching.

Discussion: <1417(dot)1466289901(at)sss(dot)pgh(dot)pa(dot)us>

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/9bc3332372f9992875d80f856fd98999e070fe35

Modified Files
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src/backend/catalog/aclchk.c | 3 ++-
src/test/regress/expected/privileges.out | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)