tell autoconf about --with-plugin options to avoid

configure: WARNING: unrecognized options: --without-plugin-xxx

config/ac-macros/plugins.m4

@@ -38,6 +38,7 @@ AC_DEFUN([_MYSQL_PLUGIN],[
   _MYSQL_PLUGAPPEND([__mysql_plugin_list__],[$1])
   m4_define([MYSQL_PLUGIN_NAME_]AS_TR_CPP([$1]), [$3])
   m4_define([MYSQL_PLUGIN_DESC_]AS_TR_CPP([$1]), [$4])
+  m4_ifdef([_AC_ENABLE_IF], [_AC_ENABLE_IF([with],[plugin-$1])])
   _MYSQL_PLUGAPPEND_META([$1], $5)
   ifelse(m4_bregexp(__mysql_include__,[/plug\.in$]),-1,[],[
      MYSQL_PLUGIN_DIRECTORY([$1],