qt_nameprep() already reset the string to its original length to
indicate failure, but we didn't handle that in qt_ACE_do(). So make it
have a return value whcih makes it easier to handle that case and do
handle it.
[ChangeLog][QtCore][QUrl] Fixed a bug that caused URLs whose hostnames
contained unassigned or prohibited Unicode codepoints to report
isValid() = true, despite clearing the hostname.
Change-Id: I41e7b3bced5944239f41fffd1545b7274c4b419d
Reviewed-by: David Faure <david.faure@kdab.com>
b0479aab29