Use new input transformation API in %%time

This avoids the perils of 'multiline specials', where valid Python syntax
unexpectedly gets turned into IPython magic commands.

Closes gh-3334

IPython/core/magics/execution.py

@@ -959,9 +959,9 python-profiler package from non-free.""")
             raise UsageError("Can't use statement directly after '%%time'!")
         
         if cell:
-            expr = self.shell.prefilter(cell,False)
+            expr = self.shell.input_transformer_manager.transform_cell(cell)
         else:
-            expr = self.shell.prefilter(line,False)
+            expr = self.shell.input_transformer_manager.transform_cell(line)
 
         # Minimum time above which parse time will be reported
         tp_min = 0.1