Add strings.h include for non-AVR platforms

Needed for strncasecmp on some platforms, like the ARC32

Author: sandeepmistry

src/WiFiMdnsResponder.cpp

@@ -22,6 +22,9 @@
 // Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
 #include <avr/pgmspace.h>
+#ifndef ARDUINO_ARCH_AVR
+#include <strings.h>
+#endif
 
 #include "Arduino.h"
 #include "WiFiMdnsResponder.h"