missing.h: explicit_bzero by SecureZeroMemory

* include/ruby/missing.h (explicit_bzero): use SecureZeroMemory on
  Windows.  assume Windows XP or later at compile time.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52826 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

include/ruby/missing.h

@@ -252,6 +252,8 @@ explicit_bzero_by_memset_s(void *b, size_t len)
     memset_s(b, len, 0, len);
 }
 #   define explicit_bzero(b, len) explicit_bzero_by_memset_s(b, len)
+# elif defined _WIN32
+#   define explicit_bzero(b, len) SecureZeroMemory(b, len)
 # endif
 #endif