Removed dart:uri since it's now a core datatype.
Removed dart:crypto import.
Updated to M5 versions of lib/http_headers.dart and lib/http_utils.dart
Added new buffer_list file/class, used by new http_headers.dart
Fix for error "Only static fields can be declared as 'const'"
Added buffer_list.dart and dart:typed_data.dart.
Added new files lib/string_transformer.dart because http_utils depend on function _decodeString() inside it.
"static const" update.
Removed const.dart and added new file http_parser.dart from M5 dart:io. Previous const objects in const are in http_parser, better to follow dart sources completly than picking out parts into new files.
Updated copyright year.
Removed _HttpParser() and _HttpDetachedIncoming leaving classes with consts, the parts that we wanted in the first place importing the file.
Added protocol version to _HttpHeaders constructor.
Updated URI syntax.
Added _HttpHeaders() protocol version.