Support EXIF data in PNGs when using GDI+

[qbnu]

Adds support for EXIF data in non-animated PNGs when ForceGDIPlus or UseEmbeddedColorProfiles is true. This is similar to what we do for JPEGs.

Example: paris_icc_exif_xmp_at_end.png

[sylikc]

Thanks for continuing to add extra EXIF support to different formats, that's very awesome, and it's definitely something I've still not been able to do

[sylikc]

i don't know what i was thinking and why i forgot to merge this in... must've been trying to implement something else late last year...