Write frames in chunks smaller than 2GB

Works around the same OpenSSL issue seen for reading except this does so
for writing. As individual frames may not be this large, this may be
less of an issue. Still this is a good preventative measure to protect
users.

distributed/comm/tcp.py

@@ -277,8 +277,13 @@ async def write(self, msg, serializers=None, on_error="message"):
                     # See <https://github.com/tornadoweb/tornado/pull/2996>
                     each_frame = each_frame.cast("B")
 
-                    stream._write_buffer.append(each_frame)
-                    stream._total_write_index += each_frame_nbytes
+                    # Workaround for OpenSSL 1.0.2 (can drop with OpenSSL 1.1.1)
+                    for i, j in sliding_window(
+                        2, range(0, each_frame_nbytes + C_INT_MAX, C_INT_MAX)
+                    ):
+                        chunk = each_frame[i:j]
+                        stream._write_buffer.append(chunk)
+                        stream._total_write_index += chunk.nbytes
 
             # start writing frames
             stream.write(b"")