Add UConverter class (ICU's UConverter API)

RFC at http://wiki.php.net/rfc/uconverter
intl: doc explaining error conventions
Fix arginfo of BreakIterator::getLocale
Improve ERROR.CONVENTIONS
Write local err on intlcal_get_time_zone() failure
Fix zpp() call in intl/converter
intl/converter in line w/ intl error handling
Make converter work on VS
Fixed paramter count