getUsersCount auth.sql: use dibi ... again

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@fiducial.net>
Stop restraining search by putting ^

The ^ was introduced in a609f723eee83a7274cc27444cc064b5ccf7057c
This broke da8e24e633c1da350c9474f3707a8c08b23d8057 (which was only taking care of sql, not ldap)
If i only remember that the login contains with "jeu", now i can search ...
Introduce regexpToLdap, and use it.

"^a" matches everything that start with a
"a$" matches everything that end with a
"^a$" matches exactly a
"a" matches everything that contains a

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@fiducial.net>