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.

util-lib: split out allocation calls into alloc-util.[ch]

util-lib: split out fd-related operations into fd-util.[ch] There are more than enough to deserve their own .c file, hence move them over.

util-lib: split our string related calls from util.[ch] into its own file string-util.[ch] There are more than enough calls doing string manipulations to deserve its own files, hence do something about it. This patch also sorts the #include blocks of all files that needed to be updated, according to the sorting suggestions from CODING_STYLE. Since pretty much every file needs our string manipulation functions this effectively means that most files have sorted #include blocks now. Also touches a few unrelated include files.

shared: add process-util.[ch]

util: rework strappenda(), and rename it strjoina() After all it is now much more like strjoin() than strappend(). At the same time, add support for NULL sentinels, even if they are normally not necessary.

remove unneeded libgen.h includes

util: replace close_pipe() with new safe_close_pair() safe_close_pair() is more like safe_close(), except that it handles pairs of fds, and doesn't make and misleading allusion, as it works similarly well for socketpairs() as for pipe()s...

namespace: include boot id in private tmp directories This way it is easy to only exclude directories from the current boot from automatic clean up in /var/tmp. Also, pick a longer name for the directories so that are globs in tmp.conf can be simpler yet equally accurate.

service: add the ability for units to join other unit's PrivateNetwork= and PrivateTmp= namespaces

systemd: use unit name in PrivateTmp directories Unit name is used whole in the directory name, so that the unit name can be easily extracted from it, e.g. "/tmp/systemd-abcd.service-DEDBIF1". https://bugzilla.redhat.com/show_bug.cgi?id=957439