hz/libtime: eliminate some unused variables

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
libtime: port to Windows, make _libtime_nanosleep always sleep for the minimum time possible

We haven't passed it any arguments > 0 because there's no reason to if we're
going for high resolution sleeps.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Makefiles: clean up, create common makefile includes

Signed-off-by: Steven Noonan <steven@uplinklabs.net>