SP_put_list_n_chars() and SP_get_list_n_chars() now
use size_t instead of long (as do the new functions
SP_put_list_n_bytes() and SP_get_list_n_bytes()).
Environment variables with a name or a value that is not proper UTF-8
are silently ignored by system:environ/2 etc.
On Mac OS X the environment variable SP_APP_DIR had the wrong
value.