MDEV-22545: my_vsnprintf behaves not as in C standard

Added parameter %T for string which should be visibly truncated.

extra/comp_err.c

@@ -787,6 +787,7 @@ static ha_checksum checksum_format_specifier(const char* msg)
       case 'x':
       case 's':
       case 'M':
+      case 'T':
         chksum= my_checksum(chksum, (uchar*) start, (uint) (p + 1 - start));
         start= 0; /* Not in format specifier anymore */
         break;