Fix bug about String#scanf("%a")
From: tarotaro0 tarousann11922960@yahoo.co.jp
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60261 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Fix bug about String#scanf("%a")
on the binary exponent. [ruby-core:82435] [Bug #13833]
[Fix GH-1689]
From: tarotaro0 tarousann11922960@yahoo.co.jp
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60261 b2dd03c8-39d4-4d8f-98ff-823fe69b080e