added new failing C++ test for using a stack allocate C++ vector inside of a generator

tests/run/cpp_vector_in_generator.pyx

+# mode: run
+# tag: cpp
+
+from libcpp.vector cimport vector
+
+def stack_vector_in_generator(vector[int] vint):
+    """
+    >>> tuple( stack_vector_in_generator([1,2]) )
+    (1, 2)
+    """
+    for i in vint:
+        yield i