Examples: Add support for custom nameserver to dnslookup

Updated dnslookup example to take an optional nameserver argument
for doing DNS lookup against a specific nameserver.

Task-number: QTBUG-30166
Change-Id: I9f46f9f766b56f770d2c8372e3bfad5c71023c73
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
compile fix if no QFileSystemWatcher is available

Change-Id: I22d0cd90da96e6b6f651768955c7f445dfbcf6bc
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Introduce proper QSurfaceFormat's setters/testers for format options

Fixes several things

* setOption(options) has the wrong name (singular)
* setOption(options) doesn't set the current options to the argument, but
ORs the current options with the argument and sets the result
* testOption(options) has the wrong name

The old methods get deprecated, and new methods and overloads get
introduced here. Old code behavior is thereby preserved.

Change-Id: I51bba49f22810c80e6b4980892600d616503af6b
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>