Fix several memory leaks, and crashes, in iconvlist(3).

• Both curitem and curitem (via the names list) was always leaked.
• malloc(3) failures lead to some leaks.
• bsd_iconv_get_list() failure lead to a crash since its error was not handles and bsd_iconv_free_list() is not NULL-safe.

I have slightly refactored this to avoid extra malloc and free logic in cases
of malloc(3) failing.

There are still bad assumptions here that I did not deal with. One of which is
that the data will always have a '/' so the strchr(3) will not return NULL.

Coverity CID: 1130055 1130054 1130053