added explicit test case for inlined context managers

tests/run/inlined_context_manager.pyx

+# mode: run
+
+cimport cython
+
+@cython.final
+cdef class TypedContextManager(object):
+    cdef double __enter__(self): # not callable from Python !
+        return 2.0
+    # FIXME: inline __exit__() as well
+    def __exit__(self, exc_type, exc_value, exc_tb):
+        return 0
+
+def with_statement():
+    """
+    >>> with_statement()
+    2.0
+    """
+    with TypedContextManager() as x:
+        return x