comctl32: fix MSVC build in imagelist.c

If I can say my opinion, I disagree on the usage of HeapAlloc/HeapFree for that known amount of memory.
Instead, for granting compatibility with MSVC, I would continue to use a structure in stack memory by simply using _alloca() and something like this:

LPBITMAPINFO bmi = (LPBITMAPINFO)
_alloca(FIELD_OFFSET(BITMAPINFO, bmiColors[256]));

or this:

LPBITMAPINFO bmi = (LPBITMAPINFO)
_alloca(sizeof(BITMAPINFO)+sizeof(RGBQUAD)*256);

and leaving all other lines of code unchanged.

Sincerely,

Carlo Bramini.
> Thomas Faber <thfabba at gmx.de> writes:
> > This removes the use of a Variable-Length Array in ImageList_CreateImage
> > and replaces it with HeapAlloc/HeapFree, as it is done in several
> > other functions in this file.
> > Alas, FIELD_OFFSET is "not const enough" for ANSI C.
>
> Using sizeof instead would be preferable.
>
> -- 
> Alexandre Julliard
> julliard at winehq.org