pgsql: Some builds (depends on crypto engine support?) of OpenSSL 0.9.7x

Log Message:
-----------
Some builds (depends on crypto engine support?) of OpenSSL
0.9.7x have EVP_DigestFinal function which which clears all of
EVP_MD_CTX.  This makes pgcrypto crash in functions which
re-use one digest context several times: hmac() and crypt()
with md5 algorithm.

Following patch fixes it by carring the digest info around
EVP_DigestFinal and re-initializing cipher.

Marko Kreen.

Tags:
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REL7_3_STABLE

Modified Files:
--------------
    pgsql/contrib/pgcrypto:
        openssl.c (r1.10.4.1 -> r1.10.4.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgcrypto/openssl.c.diff?r1=1.10.4.1&r2=1.10.4.2)