minor, provide fltdef.[ch] in analogy to strdef.[ch]

Which is to provide echs_open_fltdef() to instantiate filters defined
in files or DSOs.

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, provide echse-filter tool to run a collection of echse streams through a filter

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, provide simple example filter DSO collect

which collects XMAS and BOXD states into xmas.

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
hygiene, kick unused inline from gq.c

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'core/filter' into next

* core/filter:
  hygiene, kick unused inline from gq.c
  minor, provide simple example filter DSO collect
  minor, provide echse-filter tool to run a collection of echse streams through a filter
  minor, provide fltdef.[ch] in analogy to strdef.[ch]