silence gcc fallthrough warnings

[fireice-uk]

Adding this magic comment will stop gcc from crying out on default settings. For more info, see:

-Wimplicit-fallthrough=n section in

https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html

NOTE: I assume the four uncommented fallthroughs are intentional - I did not verify code correctness.

[zeromus]

This is gross. you should use attribute((fallthrough)) instead after defining it to something else with a GNUC check.

[fireice-uk]

Indeed, I'm just taking the path of least resistance here. I'm happy to rewrite to whatever attribute system is requested (if we are going to go that route defining one for clang might be pointful).