pgsql: Forbid gen_random_uuid() with --disable-strong-random

Forbid gen_random_uuid() with --disable-strong-random

Previously, gen_random_uuid() would fall back to a weak random number
generator, unlike gen_random_bytes() which would just fail. And this was
not made very clear in the docs. For consistency, also make
gen_random_uuid() fail outright, if compiled with --disable-strong-random.

Re-word the error message you get with --disable-strong-random. It is also
used by pgp functions that require random salts, and now also
gen_random_uuid().

Reported by Radek Slupik.

Discussion: https://www.postgresql.org/message-id/20170101232054.10135.50528@wrigleys.postgresql.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/bf723a274cbb00c7fba66c66312a77940af13d79

Modified Files
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contrib/pgcrypto/expected/pgp-compression_1.out | 8 ++--
contrib/pgcrypto/expected/pgp-decrypt_1.out | 4 +-
contrib/pgcrypto/expected/pgp-encrypt_1.out | 46 +++++++++++-----------
contrib/pgcrypto/expected/pgp-pubkey-encrypt_1.out | 12 +++---
contrib/pgcrypto/pgcrypto.c | 10 ++---
contrib/pgcrypto/px.c | 2 +-
6 files changed, 41 insertions(+), 41 deletions(-)