Spirit V2.4.2

Added keyword indexes for Spirit.Qi and Spirit.Karma to the docs.
Introduced a new customization point traits::assign_to_container_from_value which is invoked for container attributes whenever an attribute value needs to be added to that container.
Replaced proto::lit (which was used to implement spirit::lit) with a separate version allowing to distinguish 'lit(foo)' from 'foo'. This should not change any semantics nor should it break exiting code.
Added the Spirit.Qi directive as<T>[] (and its string specializations as_string[] and as_wstring[]) enabling asignment of container attribute types as a whole.
Added the Spirit.Karma directive as<T>[] (and its string specializations as_string[] and as_wstring[]) enabling handling of container attribute types during output generation as a whole.
In Spirit.Qi, lit() can now be used for numeric literals as well.
The symbols<> parser component now has an explicit name used for error handling and debugging, which can be set using the new member functions sym.name(...). Thanks to teajay for contributing a patch.
The symbols<Attrib, T> generator component now has an explicit name used for error handling and debugging, which can be set using the new member functions sym.name(...).

Fixed a problem in handling container attributes for Spirit.Qi sequences, which caused the properly parsed attributes of the first elements being overwritten by later elements of the sequence.
Fixed the Spirit.Karma generator string(s). It succeeded even if s matched only a prefix of its attribute.

Added qi::tokenid() primitive parser allowing to match arbitrary lexer tokens based on a given token id. The difference to qi::token() is, that it exposes as its attribute the token id of the matched token (instead of the iterator_range of the matched input, as qi::token() does).
Added an additional template parameter to the default lexertl::token<> definition: the type of the token id. This type defaults to std::size_t. Any type used as the id type needs to be (explicitly) convertible from std::size_t.
It's now possible to attach lexer semantic actions to token definitions based on lex::char() and lex::string().
It's now possible to specify a lexer state the lexer should automatically be switched to after matching certain tokens. For this reason the token definition syntax has been extended:
```
template <typename Lexer>
struct lexer : lex::lexer<Lexer>
{
    lexer()
    {
        int_ = "[1-9][0-9]*";
        this->self("INITIAL", "TARGETSTATE") = int_;
    }
    lex::token_def<int> int_;
};
```
This example lexer will match a int_ token and will switch the lexer to the state "TARGETSTATE" afterwards. If the second argument is not specified the lexer remains in the previous state (as before).
The parser primitives qi::token and qi::tokenid can now be used without any argument. In this case they will match any token.
lex::lit() has been removed.

Fixed an issue in the Lexer giving problems while assigning tokens to all lexer states at once. This is now possible by simply using "*" as the state name. For instance this will add the token int_ to all lexer states:
```
template <typename Lexer>
struct lexer : lex::lexer<Lexer>
{
    lexer()
    {
        int_ = "[1-9][0-9]*";
        this->self("*") = int_;
    }
    lex::token_def<int> int_;
};
```
Note: the self("*") = ... must be executed after all lexer states have been introduced to the lexer object.
Fixed lexer lookahead. The lookahead operation is now evaluated using the lexer state the token_def instance used as its argument is associated with.
Fixed a problem in the multi_pass iterator causing wrong tokens to be returned to the user. This could happen in conjunction with a lexer which performed lexer state changes and was using pass_fail in semantic actions to make a token match fail.

Spirit.Qi integer literals (like int_(10)) consume input on failure, which can lead to problems with the alternative operator.

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