Merge branch 'feature/add_sntp_sntp_h' into 'master'

Add extra "sntp/sntp.h" to be same as esp-idf

See merge request sdk/ESP8266_RTOS_SDK!429

components/lwip/component.mk

@@ -2,9 +2,10 @@
 # Component Makefile
 #
 COMPONENT_ADD_INCLUDEDIRS += include/lwip/apps \
+                             include/lwip \
                              lwip/src/include \
-                             port/esp8266/include \
-                             lwip/src/include/posix
+                             lwip/src/include/posix \
+                             port/esp8266/include
 
 COMPONENT_SRCDIRS += apps/dhcpserver \
                      apps/multi-threads \

components/lwip/include/lwip/apps/sntp/sntp.h

@@ -0,0 +1,15 @@
+// Copyright 2018-2019 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "lwip/apps/sntp.h"