* error.c (rb_exc_new, rb_exc_new_str): instantiate exception
  object directly without Exception.new method call.

Redefinition of class method `new` is an outdated style, and
internal exceptions should not be affected by it.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62500 b2dd03c8-39d4-4d8f-98ff-823fe69b080e