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 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.

sd-bus: introduce new match type "arg0has=" for matching arrays of strings Previously, sd-bus inofficially already supported bus matches that tested a string against an array of strings ("as"). This was done via an enhanced way to interpret "arg0=" matches. This is problematic however, since clients have no way to determine if their respective implementation understood strv matches or not, thus allowing invalid matches to be installed without a way to detect that. This patch changes the logic to only allow such matches with a new "arg0has=" syntax. This has the benefit that non-conforming implementations will return a parse error and a client application may thus efficiently detect support for the match type. Matches of this type are useful for "udev"-like systems that "tag" objects with a number of strings, and clients need to be able to match against any of these "tags". The name "has" takes inspiration from Python's ".has_key()" construct.

sd-bus: suppress installing local bus matches server side Matches that can only match against messages from the org.freedesktop.DBus.Local service (or the local interfaces or path) should never be installed server side, suppress them hence. Similar, on kdbus matches that can only match driver messages shouldn't be passed to the kernel.

sd-bus: introduce sd_bus_slot objects encapsulating callbacks or vtables attached to a bus connection This makes callback behaviour more like sd-event or sd-resolve, and creates proper object for unregistering callbacks. Taking the refernce to the slot is optional. If not taken life time of the slot will be bound to the underlying bus object (or in the case of an async call until the reply has been recieved).

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.