AC_DEFUN([AC_PLUGINS],[  maybe_plugins=no  AC_CHECK_HEADERS([dlfcn.h], [maybe_plugins=yes], [], [AC_INCLUDES_DEFAULT])  AC_CHECK_HEADERS([windows.h], [maybe_plugins=yes], [], [AC_INCLUDES_DEFAULT])   AC_ARG_ENABLE([plugins],    AS_HELP_STRING([--enable-plugins], [Enable support for plugins]),    [case "${enableval}" in      no) plugins=no ;;      *) plugins=yes         if test "$maybe_plugins" != "yes" ; then	   AC_MSG_ERROR([Building with plugin support requires a host that supports dlopen.])	 fi ;;     esac],    [plugins=$maybe_plugins]  )  if test "$plugins" = "yes"; then    AC_SEARCH_LIBS([dlsym], [dl])  fi])