Manually rename some symbols to again get the os-distinction

which was lost in the big renaming procedure:

ap_canonical_filename       ap_os_canonical_filename
ap_is_path_absolute         ap_os_is_path_absolute
ap_escape_path              ap_os_escape_path
ap_dso_handle_t             ap_os_dso_handle_t
ap_dso_error          -->   ap_os_dso_error
ap_dso_sym                  ap_os_dso_sym
ap_dso_unload               ap_os_dso_unload
ap_dso_load                 ap_os_dso_load


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80890 13f79535-47bb-0310-9956-ffa450edef68