The assembly code generated by MSVC for at least some signed comparisons
involving atomic variables incorrectly uses unsigned conditional jumps
instead of signed ones.  In particular, the checks in isc_log_wouldlog()
are affected in a way which breaks logging on Windows and thus also all
system tests involving a named instance.  Work around the issue by
assigning the values returned by atomic_load_acquire() calls in
isc_log_wouldlog() to local variables before performing comparisons.