Import lwIP contrib rep

... from http://git.savannah.gnu.org/cgit/lwip/lwip-contrib.git/ into contrib/ subdir, STABLE-2_1_0_RELEASE tag
lwIP contrib is now officially frozen
TODO: Fix build

contrib/ports/win32/pcapif.h

@@ -0,0 +1,32 @@
+#ifndef LWIP_PCAPIF_H
+#define LWIP_PCAPIF_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "lwip/err.h"
+
+/** Set to 1 to let rx use an own thread (only for NO_SYS==0).
+ * If set to 0, ethernetif_poll is used to poll for packets.
+ */
+#ifndef PCAPIF_RX_USE_THREAD
+#define PCAPIF_RX_USE_THREAD !NO_SYS
+#endif
+#if PCAPIF_RX_USE_THREAD && NO_SYS
+#error "Can't create a dedicated RX thread with NO_SYS==1"
+#endif
+
+struct netif;
+
+err_t pcapif_init    (struct netif *netif);
+void  pcapif_shutdown(struct netif *netif);
+#if !PCAPIF_RX_USE_THREAD
+void  pcapif_poll    (struct netif *netif);
+#endif /* !PCAPIF_RX_USE_THREAD */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* LWIP_PCAPIF_H */