mruby/mruby — pull request #625 by skandhas (2012-12-13 07:04:27+00:00)
Title: fix incorrect integer-overflow checkups in OP_SUB/OP_SUBI case.

The integer-overflow checkups in OP_SUB/OP_SUBI case is incorrect.

Ruby 1.9.x output:
``` ruby
1.class # => Fixnum
2.class # => Fixnum
-1.class # => Fixnum
(1 - 2).class # => Fixnum
(-2 + 1).class # => Fixnum
```

But, mruby output:
```ruby
1.class # => Fixnum
2.class # => Fixnum
-1.class # => Fixnum
(1 - 2).class # => Float ! !
(-2 + 1).class # => Fixnum
```