build files for qt 4.8.6 & reversed-color icons

Hi QCad developers,

I made these two little additions to the QCad code, it might be of interest to you. I'm using the "pull request" mechanism to inform you, but I'm not asking for it to be merged, this is only notifying you. Do not hesitate to close/cancel this pull request without doing nothing.

The first (commit aae16f9) is simply the necessary qmake files to build with qt 4.8.6 (current on debian testing), it is simply copied/adapted from the 4.8.5 folder

The second (commits 2b0b5a4 and 96c94b2) introduce reversed-color icons, for display on white-on-black desktop themes. I converted most of them automatically, with a python script I wrote ( http://yorik.uncreated.net/guestblog.php?2014=65 )

Hope it is of any use, thanks a lot for the wonderful work on qcad and maintaining it open source. I hope to contribute with more serious stuff in the future.

Cheers
Yorik