Merge branch 'mh/string-list'

Merge branch 'mh/string-list'

* mh/string-list:
  api-string-list.txt: initialize the string_list the easy way
  string_list: add a function string_list_longest_prefix()
  string_list: add a new function, string_list_remove_duplicates()
  string_list: add a new function, filter_string_list()
  string_list: add two new functions for splitting strings
  string_list: add function string_list_append_nodup()