Add support for U-label IDN display and processing
International domain names as standardized in IDNA2008 define both
A-label (ASCII conversion in format xn—*) and U-label (Unicode glyphs).
While the A-label is used for transport, the user should be always
presented with U-labels.
As IDNs are becoming more frequent, the presentation should be improved.
Author: Radko Krkoš krkos@cesnet.cz