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: move more file I/O related calls into fileio.[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.

util: introduce safe_fclose() and port everything over to it Adds a coccinelle script to port things over automatically.

sd-bus: introduce new SD_BUS_VTABLE_PROPERTY_EXPLICIT flag This allows marking properties as "explicit". Properties marked like this are included in the introspection, but are avoided in GetAll() property queries, PropertiesChanged() signals and in in GetManaged() object manager calls and InterfacesAdded() signals. Expensive properties may be marked that way, and they will be retrievable when explicitly being requested, but never in "blanket" all-property queries and signals. This flag may be combined with the flags for "const" and "emit-validation" properties, but not with "emit-validation", as that is only useful for properties whose value shall be sent in "blanket" all-property signals. The "explicit" flag is also exposed in the introspection data via a new annotation.

tree-wide: port everything over to fflush_and_check() Some places invoked fflush() directly with their own manual error checking, let's unify all that by using fflush_and_check(). This also unifies the general error paths of fflush()+rename() file writers.

remove unused includes This patch removes includes that are not used. The removals were found with include-what-you-use which checks if any of the symbols from a header is in use.

libsystemd: split up into subdirs We still only produce on .so, but let's keep the sources separate to make things a bit less messy.