Use FALLTHROUGH annotation to fix -Wimplicit-fallthrough warning
Use FALLTHROUGH annotation to fix -Wimplicit-fallthrough warning

Using a form that passes -Wimplicit-fallthrough=4.
See https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gcc/Warning-Options.html#index-Wimplicit-fallthrough

keplerproject/lua-compat-5.3