pgsql: Diagnose incompatible OpenLDAP versions during build and test.

Diagnose incompatible OpenLDAP versions during build and test.

With OpenLDAP versions 2.4.24 through 2.4.31, inclusive, PostgreSQL
backends can crash at exit.  Raise a warning during "configure" based on
the compile-time OpenLDAP version number, and test the crash scenario in
the dblink test suite.  Back-patch to 9.0 (all supported versions).

Branch
------
REL9_1_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/81af4185ad0c7e7868949b44878ad94522a75824

Modified Files
--------------
configure                          |   77 ++++++++++++++++++++++++++++++++++++
configure.in                       |   29 ++++++++++++++
contrib/dblink/Makefile            |    4 +-
contrib/dblink/expected/.gitignore |    1 +
contrib/dblink/expected/dblink.out |   23 +++++++++++
contrib/dblink/input/paths.source  |   14 +++++++
contrib/dblink/output/paths.source |   11 ++++++
contrib/dblink/pg_service.conf     |    7 ++++
contrib/dblink/sql/.gitignore      |    1 +
contrib/dblink/sql/dblink.sql      |   24 +++++++++++
src/test/regress/regress.c         |   46 +++++++++++++++++++++
11 files changed, 236 insertions(+), 1 deletion(-)