minor, store the whole last event instead of just the instant

This is to filter out equal events coming from 2 different streams.

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, slightly optimise __events_eq_p()

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

* tool/echse:
  minor, slightly optimise __events_eq_p()
  minor, store the whole last event instead of just the instant
Merge branch 'next'

* next:
  minor, slightly optimise __events_eq_p()
  minor, store the whole last event instead of just the instant
  chore, compile echs-filter into DSO
  chore, also kick unused __identity filter
  minor, rename echse-filter to echs-filter and kick standalone stuff
  chore, don't build echse-filter tool (echse(1) has --filter now)
  minor, support --filter in echse tool
  minor, provide service {make,free}_echs_filtstrm() in fltdef.c
  chore, provide guards for echse-filter's standalone mode and compile the binary that way
  minor, refactor echse-filter again in standalone mode
  minor, refactor filter tool so that a filter in turn is turned into a stream
  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]