Remove non-existent function from header

This is a leftover from the QGL->QOpenGL migration, the function
never existed in the QOpenGL variant of the class.

Change-Id: I47bdfb7f65ffc6cdd39b353e3a69900ccf10e4fc
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
QNativeSocketEngine(UNIX): Report the native socket error, not the Qt-derived error

This prevents error reporting from being useless in case an errno value isn't
one we anticipate.

Change-Id: I65f8c2570d07971a06ba3687d75e9df91a0e7611
Reviewed-by: Richard J. Moore <rich@kde.org>