perform, improve speed of terms by inlining mb_width() and mb_class()

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, support n-grams in terms(1) through -n|--ngram

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'feat/terms-ngrams'

* feat/terms-ngrams:
  minor, support n-grams in terms(1) through -n|--ngram
  perform, improve speed of terms by inlining mb_width() and mb_class()