Merge r574456, r720496 and r720500 from trunk:

Run optipng[1] with -o7 over all PNG files.  Files were only modified if the optimized version is smaller.  There is no change to the rendering as seen by users.

Update 'icons/apache_pb2' images for Apache-2.2

Delete the images from docroot/.
These are not needed after r105393.
The same images are still in icons/.

[1] - http://optipng.sourceforge.net/

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@720751 13f79535-47bb-0310-9956-ffa450edef68