Changed:
  char *os_get_config_path(const char *name);

To:
  int os_get_config_path(char *dst, size_t size, const char *name);

Also added:
  char *os_get_config_path_ptr(const char *name);

I don't like this function returning an allocation by default.
Similarly to what was done with the wide character conversion functions,
this function now operates on an array argument, and if you really want
to just get a pointer for convenience, you use the *_ptr version of the
function that clearly indicates that it's returning an allocation.