Don't include <sys/time.h> if WINDOWS_TIMER is set

If WINDOWS_TIMER is set, windows.h is supposed to be used instead,
and sys/time.h isn't available.

This reduces the amount of duplicated include directives in the test
apps.

Change-Id: I223d80c4ccaed2aab55e3aae66dab903ecacef7a
6 files changed