at_v0.19_14_10_30

[Admin]

Please do NOT use this old version AT, use the latest firmware instead.
请勿使用本旧版本 AT，建议使用 最新发布固件。

Notice:
AT demo v0.19 is based on SDK v0.9.2.

Details of AT update:
1. Remove at_recvTask from uart0_rx_intr_handler
2. Add uart data receiving time out.
3. Add FIFO length
4. Revise usage of ETS_UART_INTR_ENABLE() & ETS_UART_INTR_DISABLE()
5. Revise recv_task

Fixed known issue:
Data transmission through AT may cause watchdog reset.

More details in "readme" file.

[ESP_Faye]

For users who don't want to compile AT source code, we offer the AT bin compiled from source code above that support upgrade as the attachment.