Just enough to reach the BuildMacContentDirectory method and the
NeedRelinkBeforeInstall methods.
In the future, those methods can be moved to cmGeneratorTarget.
This fixes bug #13797.
The kinds of changes applied in 373faae5 for frameworks are now
applied to CFBundle. The prefix and suffix for CFBundles are
now handled in cmTarget::GetFullNameInternal.
Make handling of directory separators consistent between
non-bundle and bundle code.
Remove xcode specific flag from cmTarget when getting install_name.
Add (more) consistent convenience functions in cmTarget to get
directories inside of bundles and frameworks to add files to.
This refactor also fixes bug #12263 where frameworks
had the wrong install name when SKIP_BUILD_RPATH.
Also make install_name for frameworks consistent between Makefile
and Xcode generator.
