Add libc++.1.dylib to the healthcheck whitelist.

This is the "new" C++ stdlib on OS X and is  a standard system package
that gecode links to. From pkgutil:

    $ pkgutil --file-info /usr/lib/libc++.1.dylib

    volume: /
    path: /usr/lib/libc++.1.dylib

    pkgid: com.apple.pkg.BaseSystemBinaries
    pkg-version: 10.9.0.1.1.1306847324
    install-time: 1382478239
    uid: 0
    gid: 0
    mode: 755

Homepage: http://libcxx.llvm.org