scpi-pps: Properly clean up acquisition session.
scpi-pps: Disable beeper during session.

At least the Rigol DP800 series trigger the beeper when changing
channels remotely. Which gets rather annoying when doing acquisition
on three channels as fast as you can.
scpi-pps: Optimize channel selection.

This avoids sending a channel selection command to the device if
the channel we're working on is already on the same underlying
output channel.
scpi-pps: Start acquisition on the first enabled channel.
Provide getters for sr_dev_inst member access
ikalogic-scanalogic2: Let the sdi getter popuplage sdi->connection_id

This fixes bug #440.
sysclk-lwla: Let the sdi getter populate sdi->connection_id

This fixes bug #441.
scpi: Populate sdi->connection_id
scpi-pps: Populate sdi->serial_num and fix hw_info mem leak
hameg-hmo: Populate sdi->serial_num
rigol-ds: Populate sdi->serial_num
yokogawa-dlm: Populate sdi->serial_num and sdi->version
Auto-set sdi->connection_id for serial devices in the getter
Allow building libsigrok without libserialport.

Since the DER EE DE-5000 driver is currently the only user of
the es51919 module and it depends on the libserialport, compile
the module only if the DER EE DE-5000 driver is enabled. This
allows libsigrok to be built without libserialport again.
Rename "SERIAL" -> "SERIES".

Use the more correct term "SERIES" for the corresponding equivalent
circuit model.
Free channel group private storage when clearing device instance.
Fix typos.
scpi-pps: Add channel probe facility to scan.

If the number and specs of the device's channels are not static, i.e.
need to be probed, this facility is needed.

Initially this will be used for the Philips PM2800 series, where only
the model returned by *IDN? is needed. However this could also be used
to do actual discovery with vendor-specific SCPI commands.
scpi-pps: Move non-standard data type processing to SCPI parser.
scpi-pps: Add support for Fluke/Philips PM2800 series.