Remove the workaround for LynxOS. [skip appveyor]

LynxOS still exists, but there are no easy means to confirm that libpcap
still compiles and works on it and whether it still requires the
workaround from 2011, so let's get rid of it to simplify the matter for
the better supported OSes.

fad-getad.c

@@ -58,22 +58,16 @@
  * we end up including both the OS's <net/bpf.h> and our <pcap/bpf.h>,
  * and their definitions of some data structures collide.
  */
-#if (defined(__linux__) || defined(__Lynx__)) && defined(AF_PACKET)
+#if defined(__linux__) && defined(AF_PACKET)
 # ifdef HAVE_NETPACKET_PACKET_H
 /* Linux distributions with newer glibc */
 #  include <netpacket/packet.h>
 # else /* HAVE_NETPACKET_PACKET_H */
-/* LynxOS, Linux distributions with older glibc */
-# ifdef __Lynx__
-/* LynxOS */
-#  include <netpacket/if_packet.h>
-# else /* __Lynx__ */
-/* Linux */
+/* Linux distributions with older glibc */
 #  include <linux/types.h>
 #  include <linux/if_packet.h>
-# endif /* __Lynx__ */
 # endif /* HAVE_NETPACKET_PACKET_H */
-#endif /* (defined(__linux__) || defined(__Lynx__)) && defined(AF_PACKET) */
+#endif /* defined(__linux__) && defined(AF_PACKET) */
 
 /*
  * This is fun.
@@ -128,7 +122,7 @@ get_sa_len(struct sockaddr *addr)
 		return (sizeof (struct sockaddr_in6));
 #endif
 
-#if (defined(__linux__) || defined(__Lynx__)) && defined(AF_PACKET)
+#if defined(__linux__) && defined(AF_PACKET)
 	case AF_PACKET:
 		return (sizeof (struct sockaddr_ll));
 #endif