In order to reduce number of operations over rb-tree and process them in
batches simultaneously, all the timers changes are temporary stored in array.
While processing of these changes, the same memory is also used for storing
pointers to postpone timers adding.
As the same block of memory has been referenced by two different types of
pointers (nxt_timer_change_t * and nxt_timer_t **), some compilers may reorder
operations with these pointers and produce broken code. See ticket #221 on
GitHub for a particular case.
Now the same "nxt_timer_change_t" structure is used in both cases.
Also, reverted the -fno-strict-aliasing flag, which has been introduced in
ef76227ec159 as a workaround for this issue.
