workaround for gcc 4.3.2 bug on lenny-x86 at -O3

The following piece of code in trnman.c:

345   trn->min_read_from=  active_list_min.next->trid;
  ...
351   active_list_max.prev= trn->prev->next= trn;
352   trid_min_read_from= active_list_min.next->min_read_from;

on 345 gcc stores active_list_min.next in %ebx
(and trn->min_read_from=[%ebx]->trid)
and on 352 it does trid_min_read_from= [%ebx]->min_read_from;
BUT active_list_min.next was changed on the line 351.
gcc doesn't notice it and continues to use the cached value.

storage/maria/trnman.c

@@ -29,6 +29,9 @@
 uint trnman_active_transactions, trnman_committed_transactions,
   trnman_allocated_transactions;
 
+#ifdef WORKAROUND_GCC_4_3_2_BUG
+volatile
+#endif
 /* list of active transactions in the trid order */
 static TRN active_list_min, active_list_max;
 /* list of committed transactions in the trid order */