StringIO: fix escaping of % with %% in #printf

Author: andrykonchin

lib/truffle/stringio.rb

@@ -87,11 +87,7 @@ def print(*args)
   def printf(*args)
     check_writable
 
-    if args.size > 1
-      write(args.shift % args)
-    else
-      write(args.first)
-    end
+    write(sprintf(*args))
 
     nil
   end

spec/tags/library/stringio/printf_tags.txt

@@ -1,5 +1,3 @@
 fails:StringIO#printf formatting other formats s does not try to convert with to_str
-fails:StringIO#printf formatting other formats % is escaped by %
 fails:StringIO#printf formatting flags # applies to format o does nothing for negative argument
 fails:StringIO#printf formatting flags # applies to formats bBxX does nothing for zero argument
-fails:StringIO#printf formatting other formats % alone raises an ArgumentError