Squashed commit of the following:

commit b6dd783
Author: Christian Ehlers <cehlers@pycom.io>
Date:   Fri Feb 15 11:24:03 2019 +0100

    Openthread Link Issue FIPY fix  (#264)

    Only reference xMeshTaskHndl if LORA_OPENTHREAD_ENABLED

commit 2833cf5
Author: Islam Wahdan <islam@pycom.io>
Date:   Fri Feb 8 21:51:54 2019 +0100

    Firmware Release Candidate v1.20.0.rc7 - Pybytes v0.9.7

    ## New Features
    * Pymesh feature added from Pygo

    ## Improvments
    * Adding do_handshake for non-blocking sockets
    * Gracefully handle EAGAIN return of Socket.write in AwsMQTT lib
    * make openthread over lora a build-time configuration option (Author: @martijnthe)
    * Added factory LTE modem reset option and  method to check UE coverage
    * Updated Pybytes lib

    ## Bug Fixes
    * Fix an issue in cleaning up user threads during of soft-reset
    * Fix issue causing Device crash when safe booting (CTRL-F) while BLE/Wlan enabled
    * LTE module bug fixes
    * Fix Makefile bug where SIPY FIPY and LOPY4 excluded secure boot

    co-authored by: @Xykon [cehlers@pycom.io](mailto:cehlers@pycom.io) and @martijnthe

commit a8a62b0
Author: Martijn Thé <martijnthe@users.noreply.github.com>
Date:   Fri Feb 1 17:15:07 2019 +0100

    build config: make openthread over lora a build-time configuration option (#253)

    Adds a make variable to disable openthread. By default it's still enabled.
    To disable it, add `OPENTHREAD=off` to the `make` invocation.
    This shaves off 160KB of the .bin, making the firmware fit in the old OTA slot of 1536KB.

Author: iwahdan88

esp32/mods/modlte.c

@@ -100,7 +100,9 @@ extern TaskHandle_t mpTaskHandle;
 extern TaskHandle_t svTaskHandle;
 #if defined(FIPY)
 extern TaskHandle_t xLoRaTaskHndl;
+#ifdef LORA_OPENTHREAD_ENABLED
 extern TaskHandle_t xMeshTaskHndl;
+#endif
 extern TaskHandle_t xSigfoxTaskHndl;
 #endif
 extern TaskHandle_t xLTETaskHndl;
@@ -316,7 +318,9 @@ static void TASK_LTE_UPGRADE(void *pvParameters){
 #if defined(FIPY)
     vTaskSuspend(xLoRaTaskHndl);
     vTaskSuspend(xSigfoxTaskHndl);
+#ifdef LORA_OPENTHREAD_ENABLED
     vTaskSuspend(xMeshTaskHndl);
+#endif
 #endif
     vTaskSuspend(xLTETaskHndl);