Improve code readability by avoiding assignments inside if()

Improve code readability by avoiding assignments inside if()

* desc.c (decode_select): Move assignment out of if() condition.
* file.c (sprinttime): Likewise.
(sys_getdirentries): Likewise.
* io.c (sys_ioctl): Likewise.
* strace.c (test_ptrace_setoptions_followfork): Likewise.
(main): Likewise.
(proc_open): Likewise.
(detach): Likewise.
(proc_poll): Likewise.
(trace): Likewise.
* syscall.c (qualify): Likewise.
(sys_indir): Likewise.
* test/procpollable.c (main): Likewise.
* test/sfd.c (main): Likewise.
* time.c (printtv_bitness): Likewise.
(sprinttv): Likewise.
(print_timespec): Likewise.
(void sprint_timespec): Likewise.
(printitv_bitness): Likewise.
* util.c (dumpstr): Likewise.
(umovestr): Likewise.
(fixvfork): Likewise.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>