ruby.h: eval ASSUME argument

* include/ruby/ruby.h (ASSUME): evaluate the argument just once
  everywhere.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51772 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

include/ruby/ruby.h

@@ -48,7 +48,7 @@ extern "C" {
 # ifdef UNREACHABLE
 #   define ASSUME(x) (LIKELY(!!(x)) ? (void)0 : UNREACHABLE)
 # else
-#   define ASSUME(x) ((void)0)
+#   define ASSUME(x) ((void)(x))
 # endif
 #endif
 #ifndef UNREACHABLE