fix failing main.mysql_client_test test on 32bit

in `ulonglong=ulong*uint` multiplication
is done in ulong, wrapping around on 32bit.

This became visible after C/C changed the
default charset to utf8, thus changing
mbmaxlem from 1 to 3.

tests/mysql_client_fw.c

@@ -768,7 +768,7 @@ static void do_verify_prepare_field(MYSQL_RES *result,
 {
   MYSQL_FIELD *field;
   CHARSET_INFO *cs;
-  ulonglong expected_field_length;
+  ulonglong expected_field_length= length;
 
   if (!(field= mysql_fetch_field_direct(result, no)))
   {
@@ -777,7 +777,7 @@ static void do_verify_prepare_field(MYSQL_RES *result,
   }
   cs= get_charset(field->charsetnr, 0);
   DIE_UNLESS(cs);
-  if ((expected_field_length= length * cs->mbmaxlen) > UINT_MAX32)
+  if ((expected_field_length*= cs->mbmaxlen) > UINT_MAX32)
     expected_field_length= UINT_MAX32;
   if (!opt_silent)
   {