[BUGFIX] Undefined constant ADODB_ASSOC_CASE

adodb (v7 only) expects constant ADODB_ASSOC_CASE to be
set. PHP 7.2 now throws warnings if constants are not
defined.
Patch defines ADODB_ASSOC_CASE in unit test setUp() if
it not has been defined before.

Change-Id: Ie338c3e871ae0eb2f8536515c65b556381bf65c3
Resolves: #83210
Releases: 7.6
Reviewed-on: https://review.typo3.org/54924


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>