QKeySequenceEdit: cleanup unused member variable

Change-Id: Ib1197aee7589be0afd0c639b362bf1c3fceffeb4
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
QtConcurrent::IterateKernel: fix a race on a cache variable

getticks() can be called concurrently, so accessing a non-atomic static long,
even when the assignment will produce the same value in evey case, constitutes
a data race.

Fixed by making 'useThreadCpuTime' atomic.

Since atomic long's might not be supported on all platforms, use an
atomic int instead. To avoid a narrowing conversion, and since we're
not interested in the return value of sysconf(), only whether it
succeeded, convert any non-error return value to 0 prior to storing
in the atomic.

Change-Id: Ic285f7801327b30ddcd9c24bf1ccee3112a447b1
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>