windowscodecs: fix ICO palette size calculation

[Damjan Jovanovic]

Changelog:
* fix ICO palette size calculation

The current code works out the ICO palette size using the
ICONDIRENTRY's bColorCount, which can apparently be wrong, resulting
in too few colours read -> wrong offset to pixels and wrong AND mask
-> badly corrupted image. Rather use the BITMAPINFOHEADER's biClrUsed
the way winemenubuilder does.

Damjan Jovanovic
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diff --git a/dlls/windowscodecs/icoformat.c b/dlls/windowscodecs/icoformat.c
index 180dbb3..8012b4e 100644
--- a/dlls/windowscodecs/icoformat.c
+++ b/dlls/windowscodecs/icoformat.c
@@ -192,7 +192,7 @@ static HRESULT IcoFrameDecode_ReadPixels(IcoFrameDecode *This)
     if (bih.biBitCount <= 8)
     {
         /* read the palette */
-        colorcount = This->entry.bColorCount ? This->entry.bColorCount : 256;
+        colorcount = bih.biClrUsed ? bih.biClrUsed : 1 << bih.biBitCount;
 
         hr = IStream_Read(This->parent->stream, colors, sizeof(RGBQUAD)*colorcount, &bytesread);
         if (FAILED(hr) || bytesread != sizeof(RGBQUAD)*colorcount) goto fail;