pgsql: Support OpenSSL 1.1.0 in 9.4 branch.

Support OpenSSL 1.1.0 in 9.4 branch.

This commit back-patches the equivalent of the 9.5-branch commits
e2838c580 and 48e5ba61e, so that we can work with OpenSSL 1.1.0 in 9.4.

(Going further back would be a good thing but will take more work;
meanwhile let's see what the buildfarm makes of this.)

Original patches by Andreas Karlsson and Heikki Linnakangas,
back-patching work by Andreas Karlsson.

Patch: https://postgr.es/m/0c817abb-3f7d-20fb-583a-58f7593a0bea@proxel.se
Discussion: https://postgr.es/m/5129.1492293840@sss.pgh.pa.us

Branch
------
REL9_4_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/bb132cddf870885a6e3af102fe2accd04e5da38a

Modified Files
--------------
configure | 75 +++++++++++++++-------
configure.in | 14 ++++-
contrib/pgcrypto/internal.c | 9 ---
contrib/pgcrypto/openssl.c | 130 ++++++++++++++++++++++++++++++---------
contrib/pgcrypto/pgcrypto.c | 2 +-
contrib/pgcrypto/pgp-s2k.c | 6 +-
contrib/pgcrypto/px-crypt.c | 2 +-
contrib/pgcrypto/px.h | 1 -
src/backend/libpq/be-secure.c | 91 ++++++++++++++++++++++-----
src/include/pg_config.h.in | 15 +++++
src/interfaces/libpq/fe-secure.c | 25 +++++---
src/interfaces/libpq/libpq-int.h | 2 +-
12 files changed, 283 insertions(+), 89 deletions(-)