bug#21465: [PATCH] CC-modes hierarchy

[Zhang Kai Yu]

This is useful feature.

For example, when user set up auto completion, since clang provides completion 
to C, C++, and Objective-C, user just setup auto completion onto the common 
hook. When user open a php file, C stuff starts to auto completion.

Also, C snippets is required in C++ and Objective-C, but do not make sense in 
php.

C++ and Objective-C contains C, however php not. There are some keywords in C 
are not keywords in php, vice versa. It has structure similar to C but totally 
different language and running environment.

IMHO we should adapt to this.