Don't be so restrictive - accept "slots" as well as "slot" in rank file

This commit was SVN r24954.

orte/mca/rmaps/rank_file/rmaps_rank_file_lex.l

@@ -80,6 +80,8 @@ rank                { orte_rmaps_rank_file_value.sval = yytext;
                      return ORTE_RANKFILE_RANK; }
 slot               { orte_rmaps_rank_file_value.sval = yytext; 
                      return ORTE_RANKFILE_SLOT; }
+slots              { orte_rmaps_rank_file_value.sval = yytext; 
+                     return ORTE_RANKFILE_SLOT; }
 
 username           { orte_rmaps_rank_file_value.sval = yytext;
                      return ORTE_RANKFILE_USERNAME; }