Problems with libpng

Some versions of libpng bomb out on line 255 of pngconf.h. To fix this, remove the two invalid lines of code from /usr/local/include/pngconf.h.

Change this:

  #    ifdef _SETJMP_H
  #      __png.h__ already includes setjmp.h;
  #      __dont__ include it again.;

to this:

  #    ifdef _SETJMP_H
  /*      __png.h__ already includes setjmp.h;
        __dont__ include it again.;*/
  #    endif