Try to avoid (void) casts by adding more ATTR_NOWARN_UNUSED_RESULT.

Marked functions parameters that are allowed to be NULL. Some APIs were also changed. The non-obvious APIs where NULL parameter was changed to "" are master_service_init() and auth_master_user_list_init(). These checks can currently be enabled only on a patched clang: http://llvm.org/bugs/show_bug.cgi?id=6786

Made IS_ATEXT*() public. --HG-- branch : HEAD

Changed .h ifdef/defines to use <NAME>_H format. --HG-- branch : HEAD

Removed message-content-parser. Instead added rfc822_parse_content_type() and rfc822_parse_content_param() to help parse such headers. --HG-- branch : HEAD

Added comments --HG-- branch : HEAD

Added rfc822_parse_mime_token() to rfc822-parser API. --HG-- branch : HEAD

Added rfc822 parser which will probably replace message_tokenizer at some point. Rewrote address parsing with the new parser. This fixes various bugs in it. --HG-- branch : HEAD