djvulibre: fix corrupt djvu output with Mavericks clang+libcxx builds
patch from: https://sourceforge.net/p/djvu/djvulibre-git/ci/2c904e0cb8314c0d2314331e5ac1eaf65a7757b4/
djvulibre: install doc/ & add test case
installs some djvu-format files so we can run a functional test on the built binaries