add ether support for mac os x (#775)

Depends on pcap (e.g. with Wireshark)
build with
#cmake .. -G"CodeBlocks - Unix Makefiles" -DBACDL_ETHERNET=ON -DBACDL_BIP=OFF -DBAC_ROUTING=OFF
run as normal user (not root) like Wireshark

CMakeLists.txt

@@ -681,6 +681,28 @@ elseif(APPLE)
     ports/bsd/datetime-init.c
     ports/bsd/mstimer-init.c
     ports/bsd/stdbool.h)
+
+  if(BACDL_ETHERNET)
+    FIND_PATH(PCAP_INCLUDE pcap.h)
+    if(NOT PCAP_INCLUDE)
+      message(WARNING "BACNET: pcap.h header file not found")
+    else()
+      message(STATUS "BACNET: pcap Include:...................\"${PCAP_INCLUDE}\"")
+    endif()
+    FIND_LIBRARY(PCAP_LIBRARIES NAMES pcap)
+    if(NOT PCAP_LIBRARIES)
+      message(WARNING "BACNET: libpcap not found")
+    else()
+      message(STATUS "BACNET: pcap Lib:.......................\"${PCAP_LIBRARIES}\"")
+    endif()
+    if(PCAP_INCLUDE AND PCAP_LIBRARIES)
+      include_directories(${PCAP_INCLUDE})
+      link_libraries(${PCAP_LIBRARIES})
+      target_sources(${PROJECT_NAME} PRIVATE
+        ports/bsd/ethernet.c
+      )
+    endif()
+  endif()
 elseif(${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD")
   message(STATUS "BACNET: building for FreeBSD")
   set(BACNET_PORT_DIRECTORY_PATH ${CMAKE_CURRENT_LIST_DIR}/ports/bsd)