> Overhaul a little the QUrl error reporting.
> Update some error messages in QUrl::errorString()
> Add Q_UNREACHABLE / Q_ASSERT to two conditions that can't happen
> Move QUrlPrivate to qurl.cpp and mark all methods as inline
> Change QUrlPrivate::setAuthority to return void
> Remove the annoying qWarning when QUrl::setPort is out of range
> Update QUrlPrivate::setScheme: EmptySchemeError never happens
> Make QUrl::errorString() usable for QtTest output in invalid URLs
> Make QUrl::toString() / toEncoded() return empty for invalid URLs
> Add two compound URL invalidity cases for isValid()
> Fix DIB image reading.