ADDED: library(http_stream): multipart_open/3 and multipart_open_next/1
implement a stream filter that translates a multipart file (using a
boundary) into a series of independent streams.
ADDED: http_parse_header_value/2 can now parse Content-Type fields into
a term media(Type/SubType, Params).
ADDED: library(http/http_multipart_plugin), providing a new framework for
processing multipart/form-data content.
Reset the encoding to octet in multipart_open_next/1.
CLEANUP: library(http/http_client).  Documentation, removed dead code,
enhanced error handling.
Replace mime plugin with new multipart plugin
Flag as deprecated.