input/csv: Fix size_t printing.
agilent-dmm: Fix blocking serial write timeout.
fluke-dmm: Fix blocking serial write timeout.
atten-pps3xxx: Fix serial port timeout.
serial: Add serial_timeout().

This calculates a proper timeout value for blocking writes on the
given serial port, for the given number of bytes. Timeout is based
on a fixed 10ms OS overhead, baud rate, data bits and stop bits.
atten-pps3xxx: Use serial_timeout().
bindings: Better error handling in enumeration get() function.

Prior to this patch a call to get() with an invalid enumeration value
would raise an exception that would, for example, terminate the python
interpreter, whereas now the exception is handled and translated into a
proper python exception.
colead-slm: Fix serial port timeout.
ols: Fix serial port timeout.
build: Require glib 2.34.
Fix sr_dev_has_option().

This wasn't taking the SR_CONF_GET/_SET/_LIST flags into account.

Thanks to Janne Huttunen for spotting this.
usb: Simplify usb_get_port_path() and fix writing into a const char *.
README: Bump glib version to 2.34.
Add two new units.

Add degrees and henrys to the list of supported units. Degree is
an unit of plane angle where one degree is 1/360th of a full circle.
Henry is the SI unit of inductance.
Add measured quantities for LCR meters.

Add parallel and serial model inductance, capacitance and resistance
for LCR meter measurements. Add also secondary quantities many LCR
meters calculate, namely dissipation factor, quality factor and phase
angle.
Add quantity and flag for difference measurements.

Add 'SR_MQ_DIFFERENCE' quantity for reporting relative difference
between the current measurement and the reference value. The value
of this quantity will normally be reported in percents. Add also
the flag 'SR_MQFLAG_REFERENCE' for indicating that the reported
value is not the current measurement but the reference value instead.
Add two new 'auto' flags.

Add flags for indicating that the meter has selected the measured
quantitiy and/or the used measurement model automatically. These
are similar to the existing auto-range flag.
Add config key for LCR meter type.

Add a config key that can be used to indicate that the device is
an LCR meter.
Add config key for output frequency.

Add a config key for getting/setting the output frequency. The value
will be an uint64 and measured in hertz.
Add pretty-printer for new units and flags.

Add support for printing henries and degrees as well as the new
reference and auto flags.