Merge pull request #1052 from fperez/pylab-fix

Fix bug in pylab support introduced in #648, and refactor the pylab/gui support to eliminate a lot of code duplication we had in a number of places. 

Now all duplicate code is gone, and the only real difference is how gui event loops are integrated, which is reduced to a single static method that each relevant class grabs from its specific machinery.

IPython/testing/iptest.py

@@ -238,8 +238,8 @@ def make_exclude():
         exclusions.append(ipjoin('parallel', 'tests', 'test_mongodb'))
 
     if not have['matplotlib']:
-        exclusions.extend([ipjoin('lib', 'pylabtools'),
-                           ipjoin('lib', 'tests', 'test_pylabtools')])
+        exclusions.extend([ipjoin('core', 'pylabtools'),
+                           ipjoin('core', 'tests', 'test_pylabtools')])
 
     if not have['tornado']:
         exclusions.append(ipjoin('frontend', 'html'))