Mark QUrl::{to,from}Punycode as deprecated since 5.0

Mark QUrl::{to,from}Punycode as deprecated since 5.0

These functions are now aliases to {to,from}Ace, which are usually
what you want. The original functions from Qt 4.0 had the wrong
semantics and wrong name. The new ones from Qt 4.2 execute the ACE
processing from IDNA (specifically, the ToASCII and ToUnicode
operations described in the RFC).

But so as not to be without tests, export the tests in unit testing
environment and test the punycode roundtrip. Note that the
tst_QUrl::idna_test_suite test tests *only* the Punycode roundtrip,
not the nameprepping.

Change-Id: I9b95b4bd07b4425344a5c6ef5cce7cfcb9846d3e
Reviewed-by: João Abecasis <joao.abecasis@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: David Faure <faure@kde.org>