C++: Make pointer declaration formatter more robust

- Abort on expanded tokens
- Abort on simple declarations starting with "class"/"struct"/"enum"
- Abort if rewritten declaration does not contain '*'/'&'

Change-Id: Ifddb6f20d6bc5c0afc3fcd1d742615198515a04c
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>