Improve PR #335 (Fix resizing loop when the Windows Classic theme ...)

Improved [PR #335](https://github.com/PCSX2/pcsx2/pull/335) by using a wrapper method.

I prevented the resizing loop at the resizeColumn function in the previous change, but the point is to prevent re-entering the sizeEvent event function, and I did it in this change.

Here is a diff of before PR #335 and this change.
https://github.com/tadatada/pcsx2/commit/16fa7f13753464d68cfa95609250fb6898aaa014