COMCTL32: Maintain an order array for header control

[Phil Krylov]

Hi,

this patch speeds up header control operations a lot, especially when a
header control contains lots of items. (In my case there were 1489 items
to be added to the header control, and this would take forever with the
old code.)

ChangeLog:

Improved header control performance by maintaining an internal order array.

-- Ph.