udev: Add the Rigol DG4000 series to the udev rules
scpi_usbtmc: does not depend on libserialport
rigol-ds: does not depend on libserialport
Use PRIu64 for format in pretty-printer.

Thanks to Marcus Comstedt for the fix.
rigol-ds: prevent config_list() to return empty g_variant

This fixes the following glib message:
$ ./sigrok-cli -d rigol-ds --show
[...]
g_variant_builder_end: assertion '!GVSB(builder)->uniform_item_types || GVSB(builder)->prev_item_type != NULL || g_variant_type_is_definite (GVSB(builder)->type)' failed
rigol-ds: remove lonely break
scpi: properly check for HAVE_RPC (which is always defined)
cem-dt-885x: Don't use char as signed type.
rigol-ds: Use correct digital channel numbers when fetching config.
sysclk-lwla: Initial driver skeleton.
sysclk-lwla: Implement support for the LWLA1034.
sysclk-lwla: Fix calculation of the running sample count.

Field 7 of the status response is actually a duration in
milliseconds at all samplerates but 125 MHz.
sysclk-lwla: Honor SR_CONF_CONN at scan time.
configure.ac: Move sysclk-lwla chunk to correct location.
configure.ac: Don't build sysclk-lwla if libusb-1.0 is not found.
sysclk-lwla: Fix probe name issue.

The g_ascii_formatd() function expects the "format" argument to start
with a '%' character, e.g. it should be "%f" or such (this is not
clearly documented in the glib API docs, but visible from the source code).

The usage of "CH%f" for example will trigger an assertion and thus make the
LWLA device unusable in practice (e.g. in PulseView on Windows no probenames
would be shown, and sampling wouldn't work).

Example:
  GLib-CRITICAL **: g_ascii_formatd: assertion 'format[0] == '%'' failed

(not exposed in all glib versions or builds of glib on all distros
apparently, some may need G_MESSAGES_DEBUG=all or other measures)

From the glib g_ascii_formatd() code:
  g_return_val_if_fail (format[0] == '%', NULL);

We now use g_snprintf() instead for simplicity. This has been tested to
fix this specific issue (i.e. the probenames now do show up in PulseView).

This closes bug #270.
add udev rule for the Rigol DS2000 series
gnuplot: proper error message when using gnuplot output without logic probe
es519xx: add missing declarations for es519xx_2400_11b_altfn
move function declarations to the appropriate header