It was never used for anything and messages in debug output already
include filenames, which can be easily grepped if there is a need
to see log messages only from a particular file.
Replace SCH_*InputFileHandler() functions with more general
SCH_*FileHandler(), where events are specified as a new parameter and
which will later support other file events, e.g. file ready for ouput
and exception.
The file handlers have two new parameters: file descriptor and event.
Run getaddrinfo()/gethostbyname() in separate thread to avoid blocking.
Only one resolving thread is running at one time, so this should work
also on systems where the functions are not thread-safe.
