lib-mail: Add message_part_has_attachment
Updated copyright notices to include the year 2018.
global: Make sure all files end with newline Fixes compiler warnings with Sun C.
lib-mail: Fix message_part_data_is_plain_7bit() Content-Type parameters weren't handled exactly right. Broken by recent changes.
lib-mail: message-part-data: Implemented message_part_data_get_filename(). Gets the message part's filename if it has any.
lib-mail: message-part-data: Renamed struct message_part_envelope_data to message_part_envelope.
lib-imap: imap-envelope: Moved imap_envelope_headers to lib-mail/message-part-data as message_part_envelope_headers.
lib-imap: imap-bodystructure: Moved message_part_data header parsing and query functions to their own module in lib-mail. Moved code from imap-bodystructure and imap-envelope.