hygiene, use generated temporary symbols in coru.h

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, give yield points and coru ctors more breathing space

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, provide test command SERIES to mux trod-directives and time series

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'cmd/series'

* cmd/series:
  minor, provide test command SERIES to mux trod-directives and time series
  minor, give yield points and coru ctors more breathing space
  hygiene, use generated temporary symbols in coru.h