Fix compilation errors on intel Mac having to do with -Wimplicit-fallthrough

[Duncan Mak]

Hello,

Here's a patch that replaces the /* fall through */ comments
with __attribute__ ((fallthrough));

I needed it to make it compile on my intel Mac running macOS 11.1 and Xcode
12.2.

hangul:microcode (master) % clang --version
Apple clang version 12.0.0 (clang-1200.0.32.27)

-- 
Duncan.

fallthrough.patch
Description: Binary data