bsd: convert netport.c to C++

Allows making ifnet a C++ class.

Reviewed-by: Glauber Costa <glommer@cloudius-systems.com>
Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

bsd/porting/netport.c → bsd/porting/netport.cc

@@ -33,8 +33,8 @@ do_copystr(const void *src, void *dest, size_t len, size_t *done)
     int err = 0;
 
     // including the terminating NUL.
-    strncpy(dest, src, len);
-    n = strnlen(dest, len);
+    strncpy((char*)dest, (const char*)src, len);
+    n = strnlen((const char *)dest, len);
 
     if (n == len) {
         // on this case, destination buf isn't null-terminated.