Bug #28333 Test "flush" tries to create a new thread - on only one platform

on PPC/Debian Linux default stack size for a thread is too big.
As we use default thread settings in mysqltest, the
thread creation fails if we create lots of threads (as it
happens in flush.test). So now stack size is explicitly specified
for the mysqltest

client/mysqltest.c

@@ -496,6 +496,10 @@ void handle_error(struct st_command*,
 void handle_no_error(struct st_command*);
 
 #ifdef EMBEDDED_LIBRARY
+
+/* attributes of the query thread */
+pthread_attr_t cn_thd_attrib;
+
 /*
   send_one_query executes query in separate thread what is
   necessary in embedded library to run 'send' in proper way.
@@ -534,7 +538,7 @@ static int do_send_query(struct st_connection *cn, const char *q, int q_len,
   cn->cur_query= q;
   cn->cur_query_len= q_len;
   cn->query_done= 0;
-  if (pthread_create(&tid, NULL, send_one_query, (void*)cn))
+  if (pthread_create(&tid, &cn_thd_attrib, send_one_query, (void*)cn))
     die("Cannot start new thread for query");
 
   return 0;
@@ -5999,6 +6003,12 @@ int main(int argc, char **argv)
   next_con= connections + 1;
   cur_con= connections;
 
+#ifdef EMBEDDED_LIBRARY
+  /* set appropriate stack for the 'query' threads */
+  (void) pthread_attr_init(&cn_thd_attrib);
+  pthread_attr_setstacksize(&cn_thd_attrib, DEFAULT_THREAD_STACK);
+#endif /*EMBEDDED_LIBRARY*/
+
   /* Init file stack */
   memset(file_stack, 0, sizeof(file_stack));
   file_stack_end=