Now setup.php detects is CFG->unicode is not set and examines

Now setup.php detects is CFG->unicode is not set and examines
DB to detect such value dinamically. Useful for installations
not using the standard installer but manually edited config.php
files.
Little TODO: modify a bit the initial config tables insets to
insert this value, avoiding to call it for each request. Coming
soon (although not mandatory for 1.6beta). Tested against both
MySQL and PostgreSQL with unicode and non-unicode DBs.