PlatformIO update with c++17

Author: Godeffroy

platformio.ini

@@ -35,31 +35,55 @@ monitor_filters =
   	esp32_exception_decoder
 
 [env:Example1_FastStartup]
+build_unflags = 
+	-std=gnu++11
 build_flags =
+	-std=c++17
+	-std=gnu++17
     -D NO_WIFI
 
 [env:Example2_Debug]
+build_unflags = 
+	-std=gnu++11
 build_flags =
+	-std=c++17
+	-std=gnu++17
     -D NO_WIFI
 
 [env:Example3_WithWifi]
+build_unflags = 
+	-std=gnu++11
 build_flags =
+	-std=c++17
+	-std=gnu++17
     -D WITH_WIFI
     -D WITH_OTA
 ;upload_protocol = espota
 ;upload_port = 192.168.137.110
 
 [env:Example4_HandleCommand]
+build_unflags = 
+	-std=gnu++11
 build_flags =
+	-std=c++17
+	-std=gnu++17
     -D NO_WIFI
 
 [env:Example5_Preferences]
+build_unflags = 
+	-std=gnu++11
 build_flags =
+	-std=c++17
+	-std=gnu++17
     -D WITH_WIFI
     -D WITH_OTA
 
 [env:Example6_Teleplot]
+build_unflags = 
+	-std=gnu++11
 build_flags =
+	-std=c++17
+	-std=gnu++17
     -D WITH_WIFI
 
 [env:Example7_SPIFFS]