- update to 0.5.2:
* map: don't penalize failed insert/erase/find operations
* str: add string comparison functions `cdada_str_ncmp` and
`cdada_str_ncmp_c`
* map: add `cdada_map_get_pos()`
* map: allow NULL ptr for val in `cdada_map_find()` to only
check for presence
* set: add `cdada_set_get_pos()`
* list: minor change in `cdada_list_get()` to use
`std::advance`
* set: fix some error path return values for first()/last()
* set: minor fix in header variable name