Removed DestCharset for LDAP backends.

The internal characterset of OTRS is always utf-8 since OTRS 3.1.
The DestCharset setting in the LDAP customer backend is thus no
longer needed.
Using DBD utf8 switch for mysql

Previously, we stamped all data as utf8 in the OTRS DB object for
MySQL databases.

However this is not needed, there is a switch in DBD::mysql which
would make sure the C code already flags it as utf8.
Mark all data from DBD::Pg as utf8.

This will mark all data coming from DBD::Pg as utf8.

Also it will convert any data from non-UTF8 to UTF8 at the driver
level, which makes sure remote databases on PostgreSQL databases
that are for instance in LATIN1 present proper data in OTRS.

See http://bugs.otrs.org/show_bug.cgi?id=10005
Fix: customer data source in non-utf8 does not work.

See http://bugs.otrs.org/show_bug.cgi?id=10005

if you have a remote data source in non-utf8 the data was not
presented correctly.

the fix is to make the database library convert the data for you;
actually MySQL already did that for us. This caused double conversion
problems.
No conversion is needed in the CustomerUser::DB and CustomerCompany::DB
backends.