hash.c: fix return value

* hash.c (hash_equal): prefer true than the result of implicit
  conversion from int returned by rb_eql() to VALUE.  [Fix GH-789]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48891 b2dd03c8-39d4-4d8f-98ff-823fe69b080e