some diacritics (spanish for now) break the enrol process.
Only German and French diacritics are supported for now by PayPal.
Functionality can be easily expanded to other characters.
It make the sanitity when $CFG->sanitise_for_paypal is enabled.
Merged from MOODLE_14_STABLE
It's not at all well-tested yet (I made a lot of changes to it just tonight)
but it's late and I am literally sick (with flu) and tired so I'm checking
this in and going to bed.
Please fix all the bugs for me. ;-)