strerror: Change SEC_E_ILLEGAL_MESSAGE description

Prior to this change the description for SEC_E_ILLEGAL_MESSAGE was OS
and language specific, and invariably translated to something not very
helpful like: "The message received was unexpected or badly formatted."

Bug: https://github.com/bagder/curl/issues/267
Reported-by: Michael Osipov

lib/strerror.c

@@ -1067,6 +1067,12 @@ const char *Curl_sspi_strerror (struct connectdata *conn, int err)
 
   if(err == SEC_E_OK)
     strncpy(outbuf, txt, outmax);
+  else if(err == SEC_E_ILLEGAL_MESSAGE)
+    snprintf(outbuf, outmax,
+             "SEC_E_ILLEGAL_MESSAGE (0x%04X%04X) - This error usually occurs "
+             "when a fatal SSL/TLS alert is received (e.g. handshake failed). "
+             "More detail may be available in the Windows System event log.",
+             (err >> 16) & 0xffff, err & 0xffff);
   else {
     str = txtbuf;
     snprintf(txtbuf, sizeof(txtbuf), "%s (0x%04X%04X)",