This change makes `RE2.match(CharSequence input, int start, int end,
...)` treat `input` as extending from `(0, input.size()]` for the
purpose of zero-width assertions. Previously, `input` was considered to
extend from `(start, end]`.

This is required when evaluating capturing groups. RE2/J re-matches the
capturing group within a previous successful match, e.g.

```
Matcher m = Pattern.compile("(he)llo").matcher("hello world");
m.find() -> true
m.group(0) -> "hello"
m.group(1) -> "he"
```

During the evaluation of the last statement, RE2/J re-evaluates the
pattern within group(0) (i.e. "hello"). Before this change, RE2/J would
consider the position after 'o' and before 'w' to be both end-of-text
and end-of-line. This would cause zero-width matchers (e.g. $) to
incorrectly match, generating erroneous group matches in some cases.

Fixes google#96, see that issue for more
information.