make code in cppscanner more readable

Change-Id: Ie7821003fa8004a21ebc5847b7f79fa40ac7fa53
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
check for defines in C++ scanner

We must ignore Q_OBJECT, Q_PLUGIN_METADATA and friends, if there's a
"define" identifier in front of them.

Change-Id: Ica198e16f1ab5855db490fd67967d31d7b3b1a06
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>