affile: wildcard support added

main idea:
wildcard file source will be a separated driver
[derived from AFFileSourceDriver]

This patch:
- keep affile_sd_notify as a common function
- encapsulates notification_handlers, which can
  be overloaded by derived classes
- on_moved should be provided by all AFFileSourceDriver

Signed-off-by: Budai Laszlo <lbudai@balabit.hu>

affile: wildcard WIP
logreader:  free PollEvents object during log_reader_free
affile: enable inotify support added