os.linux: Add Linux-specific static definitions

os.linux: Add Linux-specific static definitions

And replace some magic numbers in KernelStateProvider with values
from this file.

It includes some LTTng-specific definitions, but since the statedump
events are handled in this plugin (and not in something lttng2.kernel)
it makes sense for now to put them there.

Change-Id: If47a13ca277a9da0220066b03024fca1f403beb4
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/43758
Reviewed-by: Hudson CI
Reviewed-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Tested-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>