Properly pluralize arrow and pick-up related strings.
Pluralize >2 clothing wear string
Pluralized pickup and drop messages
Pluralize monster names

This adds a new field “name_plural” to monsters, for the English plural of monster names.
Currently plural forms of monster names are used very rarely but this may change in the future.
Make monster plurals translatable
Pluralize fish names
Pluralize monster names of kill log in memorial
Apply suggestions from BevapDin
Fix English plural forms of some items
Merge remote-tracking branch 'dda/pr/7429' into dda-master

* dda/pr/7429:
  Fix English plural forms of some items
  Apply suggestions from BevapDin
  Pluralize monster names of kill log in memorial
  Pluralize fish names
  Make monster plurals translatable
  Pluralize monster names
  Pluralized pickup and drop messages
  Pluralize >2 clothing wear string
  Properly pluralize arrow and pick-up related strings.
Teensy pluralization fix, English is weird.
Make mtype::nname() a regular method, no need for it to be virtual.