Miscellaneous fixes for the OS X port.

configure.in

@@ -101,7 +101,10 @@ AC_CHECK_FUNC(nanosleep,,[
 ])
 AC_CHECK_FUNCS(usleep)
 AC_CHECK_FUNC(inet_aton,,[
-  AC_CHECK_LIB(resolv,inet_aton,LIB_VLC="${LIB_VLC} -lresolv")
+  AC_CHECK_LIB(resolv,inet_aton,LIB_VLC="${LIB_IPV4} -lresolv")
+])
+AC_CHECK_FUNC(textdomain,,[
+  AC_CHECK_LIB(intl,textdomain,LIB_VLC="${LIB_VLC} -lintl")
 ])
 AC_CHECK_FUNCS(vasprintf)
 AC_CHECK_FUNCS(swab)
@@ -1528,6 +1531,15 @@ AC_ARG_ENABLE(plugins,
      PLUGINS=
    fi])
 
+dnl Automagically disable plug-ins if there is no system support for .so files
+if test x$ac_cv_header_dlfcn_h = xno -a x$ac_cv_header_image_h = xno
+then
+  echo "*** Your system doesn't have plug-in support. All plug-ins will be compiled"
+  echo "as built-in"
+  BUILTINS="${BUILTINS} ${PLUGINS}"
+  PLUGINS=
+fi
+
 dnl
 dnl  Stuff used by the program
 dnl