Need extern before MODULE_VAR_EXPORT in order to avoid declaring object

in every file.  Some compiler/linkers won't treat these as "common"
style declarations and will complain about multiple-defns.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@78792 13f79535-47bb-0310-9956-ffa450edef68