Bug 13264: Refactor search utf8 tests and add some more

Bug 13264: Refactor search utf8 tests and add some more

t/db_dependent/www/search_utf8.t and
t/db_dependent/www/intranet_search_utf8.t were quite similar, I merged
them into a single file (t/db_dependent/www/search_utf8.t).
On the way, I added some tests for them.

Note that you will need the last patch on branch bug_11944 to see the
tests pass.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>