Implement logged_in_users.

Fixes #9.
Refactoring getHostIdentifier and adding some extra logging
clang-format on the codebase

Periodic clang-format run.
can't format filesystem_tests because of raw strings
fixing two missing semi-colon issues with clang-format
manual fix to spacing issue
Merge pull request #486 from facebook/clang-format

clang-format on the codebase
Merge pull request #497 from facebook/host-ident-sig

Refactoring getHostIdentifier and adding some extra logging
build tooling

adding build files for some random build systems
Merge pull request #501 from facebook/fbcode

build tooling
update TARGETS
TARGETS updates
Merge pull request #493 from wxsBSD/issue_9

Implement logged_in_users.
Towards predicate constraint checking
Organizing affinity types into tables.
Updating table generators to use QueryContext
Rebuild generated files when templates change.
Predicate constraints for Linux
Predicate constraints for FreeBSD
Improve kextstat/startup_items code and perf