encfs: fixes for osx 10.9

- switch to osxfuse from fuse4x
- better build flags generation
- fix boost linkage issues (used inreplace instead of big patch in original pull request)
- fix symlinks on osx

credits goes to:
defunctzombie (https://github.com/mxcl/homebrew/pull/24017)
ollyjinx (https://github.com/jollyjinx/encfs.macosx/commit/955de8e93e5dccb0406078da379a05e4bad02de9)