Add needed include for BeOS BONE builds.

Thanks to maz@albany.net (Matthew Zahorik) for the patch.
Bug #71681 r=darin

netwerk/dns/src/nsDnsService.cpp

@@ -74,6 +74,10 @@ typedef struct nsLookupElement {
 } nsLookupElement;
 #endif /* XP_MAC */
 
+#if defined(XP_BEOS) && defined(BONE_VERSION)
+#include <arpa/inet.h>
+#endif
+
 // UNIX
 // XXX needs implementation