D-BUS Configuration API v2
----------------------------

The X server will register the bus name org.x.config.displayN, and the 
object /org/x/config/N, where N is the display number.

Currently only hotplugging of input devices is supported.

org.x.config.input:
    org.x.config.input.version:
        Returns one unsigned int32, which is the API version.

    org.x.config.input.add:
        Takes an argument of key/value option pairs in arrays, e.g.:
         [ss][ss][ss][ss]
        is the signature for four options.  These options will be passed
        to the input driver as with any others.
        Option names beginning with _ are not allowed; they are reserved
        for internal use.

        Returns a number of signed int32s.  Positive integers are the
        device IDs of new devices; negative numbers are X error codes,
        as defined in X.h.  BadMatch will be returned if the options
        given do not match any device.  BadValue is returned for a malformed
        message.  (Example: 8 is new device ID 8; -8 is BadMatch.)

        Notably, BadAlloc is never returned: the server internally signals
        to D-BUS that the attempt failed for lack of memory.

    org.x.config.input.remove:
        Takes one uint32 argument, which is the device ID to remove, i.e.:
         u
        is the signature.

        Returns one signed int32 which represents an X status as defined in
        X.h. See org.x.config.input.add. Error codes are negative numbers.

    org.x.config.input.listDevices:
        Lists the currently active devices. No argument. 
        Return value is sequence of [<id> <name>] [<id> <name>] ..., i.e. [us].
