[ruby/stringio] Development of 3.1.8 started.

ruby/stringio@14fbdcc02c

Author: kou

ext/stringio/stringio.c

@@ -13,7 +13,7 @@
 **********************************************************************/
 
 static const char *const
-STRINGIO_VERSION = "3.1.7";
+STRINGIO_VERSION = "3.1.8";
 
 #include <stdbool.h>