Use mlang charset conversion in RFC2047 parser
* src/rfc2047parse.c (rfc2047_decode_tokens): Use malang-charset conversion. (_rfc2047_token, rfc2047_token_new_encoded_word): Unconstify charset. (rfc2047_token_free): New. Also free charset. (rfc2047_tokens_free): Use token_free. (g_mime_utils_header_decode_phrase): Cleanup redundant code. (rfc2047_parse): Ditto.
At least with a latin1 encoded mail from Kmail this worked and
it's probably the same conversion Outlook uses internally so
his should support everything that outlook supports.