pgpool: Fix broken scram-sha-256 authentication on big-endian machies.

Fix broken scram-sha-256 authentication on big-endian machies.

When scram-sha-256 authentication is performed, a hash function
pg_sha_256_final is used. It was imported from PostgreSQL and it uses
preprocessor define WORDS_BIGENDIAN to judge host machine's
endianness. Although WORDS_BIGENDIAN should be defined while
configure, this part was missed when pg_sha_256_final (and others) was
imported from PostgreSQL. As a result, scram-sha-256 worked only in
little endian machines. This commit fixes the issue by adding
AC_C_BIGENDIAN macro to configure.ac.

Author: Tatsuo Ishii
Reported-by: Christoph Berg
Reviewed-by: pranavkaruvally
Discussion: https://github.com/pgpool/pgpool2/issues/106
Backpatch-through: v4.2

Branch
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V4_3_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=fa7761b3a088acbc20cabf82519fe6de8abc9740

Modified Files
--------------
configure | 224 ++++++++++++++++++++++++++++++++++++++++++++++++
configure.ac | 2 +-
src/include/config.h.in | 15 ++++
3 files changed, 240 insertions(+), 1 deletion(-)