Remove usage of <stout/preprocessor.hpp> from stout.

Review: ATTENTION: default value of option force_s3tc_enable overridden by environment.
Remove usage of <stout/preprocessor.hpp> from libprocess.

Review: ATTENTION: default value of option force_s3tc_enable overridden by environment.
Remove usage of <stout/preprocessor.hpp> from mesos.

Review: ATTENTION: default value of option force_s3tc_enable overridden by environment.