[R-SIG-Mac] libpng update fixes Cairo background issues

[Simon Urbanek]

There was a bug in libpng 1.5.2 that produced corrupted RGB24 png images. The main symptom was visible in Cairo: if you specified fully opaque background color then the colors of the image would be all wrong. This is now fixed by updating libpng to 1.5.8 on the CRAN build machine. If you encounter the problem, please re-install Cairo, png or R-patched tomorrow depending where you encountered the problem (use http://r.research.att.com as the mirror for packages - CRAN mirrors should follow later).

PS: Some good soul reported this problem yesterday -- and the e-mail got lost (IMAP issues..) so if that good soul happens to read this, please reply to me.

Thanks,
Simon