premultiplied alpha for PNG,TGA,WEBP,RAW_DATA
no need for handling RAW_DATA
we are only udpating PNG now.
not treat warnings as error
Merge pull request #6961 from minggo/treat-warning-as-error

not treat warnings as error
Merge pull request #6954 from visiblelight/AlphaIssues

Make PNG files premultiplied alpha when loading
[ci skip]