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.

user-sessions: make sure /run/nologin has correct SELinux label

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.

tree-wide: drop {} from one-line if blocks Patch via coccinelle.

tree-wide: make use of log_error_errno() return value Turns this: r = -errno; log_error_errno(errno, "foo"); into this: r = log_error_errno(errno, "foo"); and this: r = log_error_errno(errno, "foo"); return r; into this: return log_error_errno(errno, "foo");

user-sessions: fix write_string_file() fallout WRITE_STRING_FILE_ATOMIC is only valid if WRITE_STRING_FILE_CREATE is also given. IOW, an atomic file write operation is only possible when creating a file is also being asked for. This is a regression from the recent write_string_file() rework.

fileio: consolidate write_string_file*() Merge write_string_file(), write_string_file_no_create() and write_string_file_atomic() into write_string_file() and provide a flags mask that allows combinations of atomic writing, newline appending and automatic file creation. Change all users accordingly.

user-sessions: move into own subdir and build independently of logind Suggested by Zbyszek on IRC. [zj: /run/nologin is used with PAM. systemd-user-session is independent of logind.]