QNX host lookup: do not try to load libresolv.so, it is not there

Not trying to load the lib saves 30 - 50ms upon an apps' 1st host
lookup.

Task-number: QTBUG-30809
(cherry picked from commit b4985215df767c14ddd888cbb2919be3a7617cfd)
Change-Id: If7338188c05f7fdf2ff80d06d91e7c7022e0e3d7
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
Avoid macro re-definition after 65bd0bd1f047f6db6d67a8f089a9a409354b95a1

based on qt5/qtbase: a9ba92740670ddbbcb0c68f80ad1a18cf2ff0598

Change-Id: Ie036d502950f5e3c0b0297d480af6cfd351e3db0
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Allow QHostInfo::lookupHost() with no receiver to warm the DNS cache.

This change lets you call QHostInfo::lookupHost() with a null receiver
in order to warm up the DNS cache. This allows you to try to get the
DNS request in flight early.

(cherry picked from commit 4030b6339c3dae4474f60b07700526fccf428b0c)

Change-Id: Ieac3c535b8f9b12a2f894510a898b349712e2fce
Reviewed-by: Richard J. Moore <rich@kde.org>
Reviewed-by: Peter Hartmann <phartmann@blackberry.com>
Increase the size of the QHostInfo cache.

This change increases the size of the DNS cache in QHostInfo from 64
entries to 128. Given the figures in the google chrome performance paper
http://www.igvita.com/posa/high-performance-networking-in-google-chrome/
this should mean we can cache enough entries to handle 4 tabs at once.

(cherry picked from commit fd9013658bab096839154ae6e68adfd1a4e10189)

Change-Id: I824aa4127b6067c3ed6a2be3dbc819288ba41d1c
Reviewed-by: Peter Hartmann <phartmann@blackberry.com>
Reviewed-by: Richard J. Moore <rich@kde.org>
SSL internals: do not write after shutting down the socket

... but rather throw an error, so the HTTP layer can recover from a SSL
shutdown gracefully. In case the other side sent us a shutdown, we tried
to send one as well, which results in an error.

(backport of commit e145b67fbd54f147dab0f8e460280a9c8533aa7b)
Change-Id: I57291a5363cb0f6585dbd6aaa521c748766a1fdf
Reviewed-by: Richard J. Moore <rich@kde.org>