According to https://pubs.opengroup.org/onlinepubs/9799919799/, the
expected behavior for the wcstombs() function is that it should
convert the wide-character codes stoping conversion either when a
character sequence exceeds the limit of n total bytes or if a null
byte is stored. In the first case, the null-terminated value should
not be appended to the dst buffer.
Currently, no null-terminator is appended to the dst buffer, even
when it's expected to be appended, generating erroneous output.
