Merge pull request #11932 from dzwillia/th-td-position-static

Added position: static to table th and td when using grid classes for sizing

less/tables.less

@@ -141,6 +141,7 @@ table {
   td,
   th {
     &[class*="col-"] {
+      position: static; // Prevent border hiding in Firefox and IE9/10 (see https://github.com/twbs/bootstrap/issues/11623)
       float: none;
       display: table-cell;
     }