[pgpool-committers: 5016] pgpool: adding support for scram authentication in health_check and sr_

[Muhammad Usama]

adding support for scram authentication in health_check and sr_check connections.

explicit backend connections in Pgpool-II uses make_persistent_db_connection(),
which use a different code path from frontend connection to authenticating with
the backend and requires its own SCRAM auth handling.
(reported by Jesper Pedersen <jesper.pedersen at redhat.com>)

Commit also fixes a problem in md5 and scram frontend authentication, where
sometimes a client was able to connect without the password.

Finally the commit also allows to connect to Pgpool-II using trust authentication
with pgpool-II even when backends requires some different authentication method.

Branch
------
SCRAM_AUTH

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=b788e74fc1b576b4827d93fcc9403502264b8541

Modified Files
--------------
src/auth/pool_auth.c | 314 ++++++++++++++++++++++++++++++++++++++++++++++-----
src/include/pool.h   |   1 +
src/protocol/child.c | 227 +------------------------------------
3 files changed, 287 insertions(+), 255 deletions(-)