[CMake] Make Uninstall

[Craig Bradney]

Hi,

I have had make uninstall working generally well in Scribus for a very  
long time now, however we had a bug submitted (http://bugs.scribus.net/view.php?id=7945 
) that indicates that the install manifest is receiving multiple  
entries for the same file, ie, two attempts at uninstall are made.

I found an updated cmake_uninstall.cmake.in to what we were using on  
the wiki, and that stops the uninstall from stopping at the duplicate  
entries, however is there a way to stop the duplicate entries  
altogether?

CMake is 2.6.3

thanks
Craig