* configure.in (-Wimplicit-fallthrough): gcc7 introduces case

fall through warnings but it is too noisy.
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=7652

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56603 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Sun Nov  6 00:03:09 2016  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* configure.in (-Wimplicit-fallthrough): gcc7 introduces case
+	  fall through warnings but it is too noisy.
+	  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=7652
+
 Sat Nov  5 23:58:32 2016  Shugo Maeda  <shugo@ruby-lang.org>
 
 	* numeric.c (rb_int_round): cast to SIGNED_VALUE to suppress

configure.in

@@ -846,6 +846,7 @@ if test "$GCC:${warnflags+set}:no" = yes::no; then
 		 -Wno-packed-bitfield-compat \
 		 -Wsuggest-attribute=noreturn \
 		 -Wsuggest-attribute=format \
+		 -Wimplicit-fallthrough=0 \
 		 $extra_warning \
 		 ; do
 	if test "$particular_werror_flags" != yes; then