Fix the following to make cpplint happy again:
- Use C++ style casts
- Rename a few header guards
- Add missing includes of standard C++ headers
- Add comments to the end of namespaces
Also, for consistency, always use "..." instead of <...> for local
include files, i.e.
#include "idmap2/.*"
Test: cmds/idmap2/static-checks.sh
Change-Id: Ie735a36d562d1fc51b61f1f0f45aec0d160f602d