Bug 1015844 - part 1, Only force the search to normal flow child lists for true overflow containers.  r=roc
Bug 1015844 - part 2, Add a call to ReflowOverflowContainerChildren() to reflow abs.pos. overflow containers.  r=roc

nsColumnSetFrame puts true overflow containers on the principal child list
(which may then get pushed to the overflow list), but overflow containers
for abs.pos. children still go on the kOverflowContainersList and
kExcessOverflowContainersList lists as usual.