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>
logreader:  free PollEvents object during log_reader_free
affile: PollEvents object can be invalidate during log_pipe_notify()
affile: poll-file changes fixed
affile: poll-file-changes refactor
filemonitor_poll: read the whole directory in every poll cycling,

because it takes too much time to step file-by-file
in case of lot of files and large follow-freq number.

Signed-off-by: Juhász Viktor <jviktor@balabit.hu>
affile: path resolving replaced by a realpath() based implementation

Signed-off-by: Budai Laszlo <lbudai@balabit.hu>
affile: enable inotify in configure.ac

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