Fix VS compiler warning.
NImage now uses NIndex for pixel indices.
Added NImage::ForEach to visit each pixel.
Added BGRX and BGRA image formats.
Added StCOM for stack-based COM initialisation.
Fix memory corruption in NDataDigest::GetSHA1.
Rename MD5 locals to match SHA1.
Pass unsigned char to isprint to avoid VC++ assertion failure.
Add support for NImage format conversion.
Replace NImage::ForEach with ForEachPixel and ForEachRow.