OSX: Warn when attempting to change runtime paths on OS X 10.5

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.

Also modifying BundleUtilities test to remove an undesirable cmake
generated runtime path.  The intent was to build with the install
rpath as is done with the other cases in this test.
Merge topic 'rpath-osx-10_6' into next

a6e58f55 OSX: Warn when attempting to change runtime paths on OS X 10.5