[BUGFIX] Improve functional test execution on Windows system

On Windows systems you can execute several commands using '&' like
set typo3DatabaseUsername=root & set typo3DatabasePassword=root.
Unfortunately Windows sets those parameter with a trailing space. This
causes database connections not to work. Therefore the patch adds a trim
on getting system environment variables for database credentials for
functional tests.

Furthermore the PHP versions on Windows throw a warning on setting the
database name when the connection is closed. The warning is caught by
PHPUnit but the database tables aren't initialized correctly. This patch
adds an '@' to mute the warning.

Releases: master, 6.2
Resolves: #64680
Change-Id: If649b5bd440a3bd504f028a3c9c96c9d294d380c
Reviewed-on: http://review.typo3.org/36491


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>