Marks the old functions as deprecated and adds new safe versions.The
new functions give access to the native descriptor safely. It also
fixes the original functions in Qt 6.

warning: implicit conversion loses integer precision: 'qintptr' (aka 'long long') to 'int'

Change-Id: I59177905af0181912d2e7824ce68265cb8ee03d9
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>