esp8266 2.3.0 compatability restored #576

asyncscannetworks not available in esp8266 2.3.0, adjusted server on to take cstr for backwards compatability

WiFiManager.h

@@ -13,6 +13,7 @@
 #ifndef WiFiManager_h
 #define WiFiManager_h
 
+#include <core_version.h>
 #include <vector>
 
 // #define WM_MDNS            // also set MDNS with sethostname
@@ -20,6 +21,11 @@
 // #define WM_ERASE_NVS       // esp32 erase(true) will erase NVS 
 // #define WM_RTC             // esp32 info page will include reset reasons
 
+#ifdef ARDUINO_ESP8266_RELEASE_2_3_0
+#warning "ARDUINO_ESP8266_RELEASE_2_3_0, some WM features disabled" 
+#define WM_NOASYNC         // esp8266 no async scan wifi
+#endif
+
 // #include "soc/efuse_reg.h" // include to add efuse chip rev to info, getChipRevision() is almost always the same though, so not sure why it matters.
 
 // #define esp32autoreconnect    // implement esp32 autoreconnect event listener kludge