Performance regression. Cpp hover in header file is now much slower

When keeping the Control key kressed while moving around the mouse, symbuls below the mouse pointer become clickable links.

That became very laggy in Qt Creator 2.1.0 compared to 2.0.1, when doing that in a header file on methonds in a class declaration. Now, it basically eats the whole CPU and becomes laggy. 2.0.1 was snappy.