pspell_store_replacement() stores a replacement pair for
a word, so that replacement can be returned by
pspell_suggest() later. In order to be able to take
advantage of this function, you have to use
pspell_new_personal() to open the dictionary. In order
to permanently save the replacement pair, you have to
use pspell_config_personal() and
pspell_config_repl() to set the path where to save your
custom wordlists, and then use pspell_save_wordlist()
for the changes to be written to disk.