Fixed #19866 -- Added security logger and return 400 for SuspiciousOperation.

SuspiciousOperations have been differentiated into subclasses, and
are now logged to a 'django.security.*' logger. SuspiciousOperations
that reach django.core.handlers.base.BaseHandler will now return a 400
instead of a 500.

Thanks to tiwoc for the report, and Carl Meyer and Donald Stufft
for review.

tests/urlpatterns_reverse/urls_error_handlers_callables.py

@@ -9,5 +9,6 @@ from .views import empty_view
 
 urlpatterns = patterns('')
 
+handler400 = empty_view
 handler404 = empty_view
 handler500 = empty_view