Merge pull request #3259 from dabroz/feature-16bitfix1

Fix for sprintf test exceeding bounds with MRB_INT16

mrbgems/mruby-sprintf/test/sprintf.rb

@@ -5,5 +5,5 @@ assert('String#%') do
   assert_equal "one=1", "one=%d" % 1
   assert_equal "1 one 1.0", "%d %s %3.1f" % [ 1, "one", 1.01 ]
   assert_equal "123 < 456", "%{num} < %<str>s" % { num: 123, str: "456" }
-  assert_equal 16, ("%b" % (1<<15)).size
+  assert_equal 15, ("%b" % (1<<14)).size
 end