Many changes/fixes to wxFlexGridSizer implementation (no API changes):
- fix the problems addressed by the patch
1667343:
* only distribute extra space between growable items, not all space
* take hidden items and gaps into account for ALL grow mode layout
* fix rounding errors by allocating the remaining pixels to the last item(s)
- refactor the code to avoid duplication between row/column cases
- use STL-like wxList methods instead of compatibility ones
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45583
c3d73ce0-8a6f-49c7-b76d-
6d57e0e08775