djvulibre: one-line patch fixing osx 10.9 breakage

djvudigital & its helpers were producing corrupt djvu files when compiled with clang
gcc builds still work properly
ghostscript (--with-djvu) still works if compiled with clang

the patch is cherry-picked from HEAD, per the sourceforge links. i suggested just switching to HEAD earlier, and that commit was passively rejected earlier in this PR. so I then spent more time to isolate this patch, as was suggested. Now I get needled as to why I did that.

when ever the maintainer for this formula shows up and updates it to the next point release (TBD), it can go away.