`LANGUAGE=C` is not enough, `LC_ALL=C` is needed as the environment
variable that overrides all the other localization settings.
e.g.
```bash
$ LANGUAGE=C id foobar
id: ‘foobar’: no such user
$ LC_ALL=C id foobar
id: 'foobar': no such user
```
* replace `LANGUAGE` with `LC_ALL` as environment variable in the tests
* fix the the date string of affected uutils
* replace `‘` and `’` with `'`
When invoked via '[' name, last argument must be ']' or we bail out with
syntax error. Then the trailing ']' is simply disregarded and processing
happens like usual.
- add `==` as undocumented alias of `=`
- handle negated comparison of `=` as literal
- negation generally applies to only the first expression of a Boolean chain,
except when combining evaluation of two literal strings
- Replace the parser with a recursive descent implementation that handles
parentheses and produces a stack of operations in postfix order.
Parsing now operates directly on OsStrings passed by the uucore framework.
- Replace the dispatch mechanism with a stack machine operating on the
symbol stack produced by the parser.
- Add tests for parenthesized expressions.
- Begin testing character encoding handling.
