Applied patch [ 598016 ] remove flicker during combo box creation

Applied patch [ 598016 ] remove flicker during combo box creation
By Benjamin I. Williams (biwillia76)

The attached patch completely fixes the flicker problem when
creating combo boxes.  It also will make it elementary to
remove flicker during the creation of other controls
(although all the other controls are flicker free, AFAIK).
It does this by adding an optional 'visible' parameter to
the internal MSWCreateControl method, whereby the caller can
create a control invisibly by default, perform some
complicated sizing calculations, and then finally show the
control before the Create finished.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@16676 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775