PushCutter should stop on request

git-svn-id: https://pycam.svn.sourceforge.net/svnroot/pycam/trunk@379 bbaffbd6-741e-11dd-a85d-61de82d9cad9

pycam/PathGenerators/PushCutter.py

@@ -135,5 +135,7 @@ class PushCutter:
 
             # update the progress counter
             if not progress_counter is None:
-                progress_counter.increment()
+                if progress_counter.increment():
+                    # quit requested
+                    break