CMake Nightly Date Stamp
OSX: Only enable @rpath support on OS X 10.6 or greater.

Even though 10.5 supports @rpath, the support is not complete
enough for CMake.  For instance, install_name_tool doesn't support
adding and removing rpaths.
Merge topic 'rpath-osx-10_6' into next

36c509b9 OSX: Only enable @rpath support on OS X 10.6 or greater.
b8f19473 CMake Nightly Date Stamp