add a compile test for github issue #1692: raising StopAsyncIteration without...

add a compile test for github issue #1692: raising StopAsyncIteration without using "await" was missing utility code and failed to compile

tests/compile/stop_async_iteration_exception_pep492.pyx

+# mode: compile
+# tag: pep492
+
+# make sure async iterators also compile correctly without using 'await'
+
+cdef class AsyncIter:
+    cdef long i
+    cdef long aiter_calls
+    cdef long max_iter_calls
+
+    def __init__(self, long max_iter_calls=1):
+        self.i = 0
+        self.aiter_calls = 0
+        self.max_iter_calls = max_iter_calls
+
+    def __aiter__(self):
+        self.aiter_calls += 1
+        return self
+
+    async def __anext__(self):
+        self.i += 1
+        assert self.aiter_calls <= self.max_iter_calls
+
+        if self.i > 10:
+            raise StopAsyncIteration
+
+        return self.i, self.i