[trunk]  not supported on OSX linkers
[trunk] Versioned filename on OSX has the version prior to the extension, unlike for Linux shared objects
[trunk] Only define a dynamic library import library output file on Windows now
[trunk] OSX clang toolchain now registers the Posix shared library symlink tool
[trunk] Dynamic library symlinks are now generated on OSX as well
[trunk] Posix shared library symlinks now have the right leafnames on OSX
[trunk] Adding current and compatibility versions on OSX dylibs
[trunk] Adding TODOs for Xcode