agilent-dmm: Shorten vendor name.
rigol-ds: Shorten vendor name.
rigol-ds: On DS1000 with firmware < 0.2.4, use legacy protocol.

Apparently the ASCII header containing length was only added in version
0.2.4.
session: Auto-commit settings before acquisition.

(sr_session_start): Just before starting acquisition on
a device, call sr_config_commit() to apply pending config
changes to the hardware device.
(sr_session_dev_add): Ditto.  Also, return an error code
if starting acquisition failed.
rigol-ds: DS1000 series still needs the stupid delay.
std: Fix caller prefix output.
Make sure to delete temporary metadata file after use.

Fixes bug 276.
fluke-dmm: Make protocol parsers locale-independent.
agilent-dmm: Make protocol parser locale-independent.
brymen-dmm: Make protocol parser locale-independent.
rigol-ds: Disable key lock when closing device.