Debug mode: mouse click on stack frame in 'Call stack' windows navigates...

... to file:line

Hello,
With this commit, it's possible to navigate between stack frames in debug mode by mouse click in "Call stack" window.

Tested only with:
   Ubuntu 13.10 x64
   gcc (Ubuntu/Linaro 4.8.1-10ubuntu9) 4.8.1
   go version go1.2.1 linux/amd64
   Qt 4.8.4