Rename the global variable `out` to `gOut` so that one can easier realize it is a global variable. Fix some comment problem.
Rename the global variable `out` to `gOut` so that one can easier realize it is a global variable.
Fix some comment problem.

postfix/go-diff,daviddengcn/go-diff,postfix/go-diff,daviddengcn/go-diff,postfix/go-diff,daviddengcn/go-diff