Comment intentional fallthrough in case statements

[kraj]

Fixes build with gcc7

Signed-off-by: Khem Raj raj.khem@gmail.com

[redboltz]

@kraj , thank you for sending the PR.
The file you modified is a part of generated code.
In order to add the comment, we need to edit erb code.

I updated your PR.
https://github.com/redboltz/msgpack-c/tree/kraj-devtool
Could you test it on your environment?

[kraj]

@redboltz yes I tested that branch and it works here.

[redboltz]

merged.