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

Put comment above and link to https://sourceforge.net/p/djvu/bugs/236/. Also, not clear to me what the resolution of that bug is?