Fix problem with windows builds mistakenly trying to include unistd.h et al.

I believe I have found a set of preprocessor macros that arranges for `unistd.h`, `sys/stat.h`, and `sys/types.h` to be included on unix and mac, but not on windows.  I have tested the fix on Linux, and everything works as expected, but having no access to a mac or windows system, I can't test there.  Please test on both windows and mac before merging this request.

Here are the behaviors expected on mac:
* The code should build successfully while including the headers mentioned above.
* If the logs directory does not exist at run time, it should be created.
* If a file (not a directory) called logs exists at run time hector should fail with the message "* Program exception: Log directory logs exists but is not a directory"
* If the logs directory exists without write permission at run time hector should fail with the message "* Program exception: Log directory logs lacks write permission."

The expected behavior on windows is:
* The code should not attempt to include any of the headers mentioned above.
* On any of the problems with the logs directory described above, hector should fail with the message "Unable to open log file".