fix width of toppager in Firefox and Chrome

Usage of `jQuery.width` on **disconnected** pager is unsafe. One have to
set `width` using `jQuery.css` like one do with the pager div or to
place toppager first on the correct place and *then* use `width`.
fix usage of wrong column headers in case of usage hidden: "true"

One posts from time to time the same problem with wrong column headers
in case of usage `hidden: "true"` instead of `hidden: true`. jqGrid hide
the column of data in the case, but don't hide the column headers. As
the result one have grid with vary strange layout. The fix uses only
boolean values of `hidden` property and the usage of `hidden: "true"`
hide nothing.
copy jquery.jqGrid.src.js,jquery.jqGrid.min.js in js directory