tree-wide: remove Emacs lines from all files This should be handled fine now by .dir-locals.el, so need to carry that stuff in every file.

core: Add machine-id setting Allow for overriding all other machine-ids which may be present on the system using a kernel command line systemd.machine_id or --machine-id= option. This is especially useful for network booted systems where the machine-id needs to be static, or for containers where a specific machine-id is wanted.

machine-id-setup: add a machine_id_commit call to commit on disk a transient machine-id If /etc was read only at boot time with an empty /etc/machine-id, the latter will be mounted as a tmpfs and get reset at each boot. If the system becomes rw later, this functionality enables to commit in a race-free manner the transient machine-id to disk.

machine-id: add --root option to operate on an alternate fs tree This makes it possible to initialize the /etc/machine-id file on an arbitrary filesystem hierarchy. This helps systems that wish to run this at image creation time in a subdirectory, or from initramfs before pivot-root is called. [tomegun: converted to using _cleanup_free_ macros]

use #pragma once instead of foo*foo #define guards #pragma once has been "un-deprecated" in gcc since 3.3, and is widely supported in other compilers. I've been using and maintaining (rebasing) this patch for a while now, as it annoyed me to see #ifndef fooblahfoo, etc all over the place, almost arrogant about the annoyance of having to define all these names to perform a commen but neccicary functionality, when a completely superior alternative exists. I havn't sent it till now, cause its kindof a style change, and it is bad voodoo to mess with style that has been established by more established editors. So feel free to lambast me as a crazy bafoon. v2 - preserve externally used headers

build-sys: move *-setup out of shared to avoid selinux being pulled in