Changed #include <linux/if.h> to #include <net/if.h>

Including linux/if.h instead of net/if.h causes conflicts with applications that use net/if.h.
Merge branch 'if_h_issue' into develop
Merge pull request #418 from teemu-kemppainen/develop

Using #include <linux/if.h> conflicts with other libraries and code that use #include <net/if.h>