Add HTTP field value parsers:

ext_list:
    Iterable container of comma separated extensions, where each extension
    is a token followed an optional list of semicolon delimited parameters,
    with each parameter consisting of a name / value pair. The value can
    be a token or quoted-string.

param_list:
    Iterable container of semicolon delimited parameters, where each parameter
    is a name / value pair. The value can be a token or quoted-string.

token_list
    Iterable container of comma delimited tokens.

* Remove obsolete rfc2616 functions

* Refactor and consolidate case-insensitive string helpers

include/beast/http/parser_v1.hpp

@@ -124,8 +124,6 @@ private:
     {
         if(! value_.empty())
         {
-            rfc2616::trim_right_in_place(value_);
-            // VFALCO could std::move
             m_.headers.insert(field_, value_);
             field_.clear();
             value_.clear();