Merge lp://qastaging/~mc-return/compiz/compiz.merge-recompress-png-resources into lp://qastaging/compiz/0.9.8

Reduces combined filesizes of Compiz' .png resources from 2.2MB to 1.5MB by recompression of those with Trimage Image Compressor.
This will decrease package size, downloading/loading/displaying times without changing appearance in any way, because png is a lossless format and this commit just optimizes compression and filesizes.
png files with higher compression take less time to display, not only because of reduced loading times, but also because deflation in memory finishes faster as decompression speed is largely uninfluenced by the compression level and thus decompression of better compressed png files is faster.

Reduces combined filesizes of Compiz' .png resources from 2.2MB to 1.5MB by recompression of those with Trimage Image Compressor.
This will decrease package size, downloading/loading/displaying times without changing appearance in any way, because png is a lossless format and this commit just optimizes compression and filesizes.
png files with higher compression take less time to display, not only because of reduced loading times, but also because deflation in memory finishes faster as decompression speed is largely uninfluenced by the compression level and thus decompression of better compressed png files is faster.

References:

According to http://www.libpng.org/pub/png/book/chapter01.html decompression speed is largely unaffected by the compression level, but that a less compressed image may take more time to read from disk (see end of chapter 1.2.4. Compression)

Also the authors suggest to use an optimizer to better compress your .png files (9.4 Practical compression tips - 9.4.1. Tips for Users - http://www.libpng.org/pub/png/book/chapter09.html)

Here you can see that quite modern hardware also decompresses crushed/optimized files faster:
http://www.cocoanetics.com/2012/03/ipad-3-image-decompression-benchmarked/

Here another recommendation to use png optimization:
http://www.cocoanetics.com/2011/10/avoiding-image-decompression-sickness/