Known bugs in libpng version 1.2.41

1. December 4, 2009: The PNG_NO_ERROR_NUMBERS macro was inadvertently
   defined in libpng-1.2.41/pngconf.h, which may cause a problem with
   building a binary-compatible library.

   STATUS: This will be fixed in libpng-1.2.42.  In the meantime, simply
   delete the definition (line 759 of pngconf.h).