Log Message:
Apply patches for the three 10.29 bugs listed on SourceForge we
hadn't already fixed. The list:

http://sourceforge.net/project/shownotes.php?group_id=5128&release_id=349291

The problems fixed in this PKGREVISION bump:

* pnmtopng: can crash due to wild pointer if you don't use the
    -alpha option.
* pammasksharpen:  Multiple bugs cause it to produce incorrect
    output.
* pnmhisteq: -rmap doesn't work.

Addresses my own PR pkg/31314, with thanks to Nathan Arthur for
bringing these patches to my attention.