fix multi_line_specials error

caused by e.g. test_prefilter/test_issue114

IPython/core/prefilter.py

@@ -695,7 +695,7 b' class AutoMagicChecker(PrefilterChecker):'
             return None
 
         # We have a likely magic method.  Make sure we should actually call it.
-        if line_info.continue_prompt and not self.shell.multi_line_specials:
+        if line_info.continue_prompt and not self.prefilter_manager.multi_line_specials:
             return None
 
         head = line_info.ifun.split('.',1)[0]