like search page, widens to 2 columns for bulk update page too
don't position "User Summary" as "absolute right" for small screens.

by default(in RT's accordion.css), position css of "User Summary" link(used in
ShowRoleMembers) is:

{
    position: absolute;
    right: 0;
}

this could result in overlapping(with the content at the left side) when the
screen is not wide enough. I tried "float: right", but then it shadows the
following contents(like "Real Name Enoch Root") below it in small screens.

using "relative" position in small screens works(no overlapping or hidding),
though it doesn't look that good(since it's not at the right side).
edge case fix so we can use 2-columns in modify pages generally.

before, it works only on Chrome, now it also works on Safari/Firefox/IE10+.
old IE still doesn't work though.