* Asynchronous interface
    Grep for (reentrant|thread) comments
* Multithreaded interface
    Grep for (reentrant|thread) comments
* Make CURL (network services) optional
* Improve isds_*message() system
    Allow formatted message appending, preserve deep messages
* Catch libxml2 debug messages
* Make function tests
    Cover all functions
    Simulate server?
* Test X.509 authentication
* Write high level documentation
    ISDS overview
    Gather comments from header files
    Write manual page(s)
* I18N
    Solve UTF-8 vs. locale-encoded logging schism
* Find a way how to request for a box creation
* Test message is system generated
* Make high logic checks optional
* Validate XML trees (optional)
* Distinguish processing errors by different isds_error values instead of
  generic IE_ERROR
    Invalid input from application (IE_INVAL?)
    Library error on processing application data
    Library error on processing server data
    Server error
