Ship LX interface headers in /usr/include/compat/linux
We deliver LX headers in /usr/include and that results in the following:
- software picks such interfaces, even though no one told them to do so
- unnecesearry suprises might pop up (https://www.illumos.org/issues/7506)
LX specific headers should be contained in /usr/include/compat/linux and if somebody wishes to use them, he should just add this path to his includes.