Correction for one Mac OS X icon file (bug 54820)

See the bottom of this bug for the summary:
https://bugs.freedesktop.org/show_bug.cgi?id=54820

I suspected as soon as I saw the behaviour, the PNGs from which the
icns file was generated specify a non-zero image offset (a.k.a.
vitrual canvas, or page). See:
http://www.imagemagick.org/Usage/basics/#page

However that does not appear to be the case:

mars:~ nickshanks$ identify main.png
main.png PNG 128x128 128x128+0+0 8-bit DirectClass 2.27KB 0.000u 0:00.019
mars:~ nickshanks$ identify main.png
main.png PNG 256x256 256x256+0+0 8-bit DirectClass 4.38KB 0.000u 0:00.000

(note the +0+0 canvas offset)
As such I don't know what caused the borders to appear, but anyway,
the file here fixes the issue:
http://web.nickshanks.com/libreoffice/revised-main-icon.tgz

Again, the file paths inside are relative to in the
core/sysui/desktop/ directory, so extracting there will overwrite the
old files. (And I gzipped it this time for all you gzip lovers out
there ;-)

The package also contains revised 512x512 and 1024x1024 icons, because
the originals were 2px and 4px too far left, respectively. When
zooming the icon size up and down, there was a perceptible jump at the
256–257px boundary. I also pngcrushed them (with -brute).

Note of caution to anyone working with PNGs on Mac OS X: Pixelmator
used an unexpected colour profile when opening an image which has no
embedded profile (might be my monitor's calibration profile?). I had
to use Acorn to move the pixels.

-- 
Nicholas.