[PATCH] gdiplus: Disable PNG encoding filters.

[Florian Will]

Thank you, Stefan and Esme! (And sorry about the other mail, Esme - I
thought gmail would reply to all by default)

> Native probably sets it based on EncoderParameters, but I think this
> is good enough for now.

I used the "Determining the Parameters Supported by an Encoder"
example code to query image/png encoder parameters on win10, and if I
understand that output correctly, the PNG encoder only supports the
"EncoderImageItems" parameter (for image metadata). Or maybe the
"EncoderQuality" parameter is supported implicitly without being
listed in GetEncoderParameterList? I haven't tried it, but Google
found a forum thread where people basically complain that gdiplus
can't use prefiltering when encoding PNG files.