gnu_java_math_GMP.c:1135:13: error: this statement may fall through [-Werror=implicit-fallthrough=]
         res = mpz_popcount (_this);
         ~~~~^~~~~~~~~~~~~~~~~~~~~~
gnu_java_math_GMP.c:1136:7: note: here
       default:
       ^~~~~~~

Signed-off-by: Guo Li <uxgood.org@gmail.com>