Connector/ODBC: SqlwcsOctetLen sizes UTF-16 with a byte-oriented helper, reading past the caller's buffer and sending client memory to the server

`SqlwcsOctetLen` (`driver/ma_platform_posix.cpp:121`) sizes a UTF-16 string by calling Connector/C's `mb_charlen`. That helper is byte-oriented: its `UTF16_HIGH_HEAD(x)` macro casts the argument to `uchar`, so it inspects only the low byte. `SqlwcsOctetLen` hands it a whole `SQLWCHAR`, so every …

/* CharLen < 0 - treat as NTS */
SQLINTEGER SqlwcsOctetLen(const SQLWCHAR *str, SQLINTEGER *CharLen)
{
  SQLINTEGER result= 0, inChars= *CharLen;

  if (str)
  {
    while (inChars > 0 || (inChars < 0 && *str))
    {
      result+= DmUnicodeCs->mb_charlen(*str);
      --inChars;
      str+= …