pgsql: Add gen_random_uuid() to contrib/pgcrypto.

Add gen_random_uuid() to contrib/pgcrypto.

This function provides a way of generating version 4 (pseudorandom) UUIDs
based on pgcrypto's PRNG.  The main reason for doing this is that the
OSSP UUID library depended on by contrib/uuid-ossp is becoming more and
more of a porting headache, so we need an alternative for people who can't
install that.  A nice side benefit though is that this implementation is
noticeably faster than uuid-ossp's uuid_generate_v4() function.

Oskari Saarenmaa, reviewed by Emre Hasegeli

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/e6170126fc201052b0ec5fc92177eb181d602d26

Modified Files
--------------
contrib/pgcrypto/Makefile               |    2 +-
contrib/pgcrypto/pgcrypto--1.0--1.1.sql |    9 ++
contrib/pgcrypto/pgcrypto--1.0.sql      |  202 ------------------------------
contrib/pgcrypto/pgcrypto--1.1.sql      |  207 +++++++++++++++++++++++++++++++
contrib/pgcrypto/pgcrypto.c             |   27 ++++
contrib/pgcrypto/pgcrypto.control       |    2 +-
contrib/pgcrypto/pgcrypto.h             |    1 +
doc/src/sgml/datatype.sgml              |    2 +
doc/src/sgml/pgcrypto.sgml              |   11 ++
doc/src/sgml/uuid-ossp.sgml             |    9 ++
10 files changed, 268 insertions(+), 204 deletions(-)