uni-t-dmm: Fix scanning, properly use new sr_usb_find().
uni-t-dmm: Expose hwopts.
Add missing "ULL" suffixes.

These numbers are larger than 32bit, mark them as ULL to avoid compile
failures on 32bit systems.
uni-t-dmm: Quickfix for UNI-T UT61D.

This is a temporary fix only, since a major rework of uni-t-dmm is being
done at the moment, soon to be merged.
serial.c: Fix copy-paste error.

Thanks Bert Vermeulen for reporting.
unify sr_datafeed_meta_* into one struct containing sr_config

struct sr_config is the new name for sr_hwopt. Its companion meta
struct, sr_hwcap_option, was renamed sr_config_info.
drivers: use new sr_config struct

Sending an SR_DF_META packet at the start of every stream is not
mandatory; the frontend should ask for what it needs, and any extra
information the driver wants to send will come in due time.
free USB config descriptor after use
Use new SR_DF_META packet.

Since input modules determine a samplerate by reading from their
file format (or having it overridden with an option), they need
to pass this up to the frontend.
Adjust option helpers to new sr_config struct
Add small helper for creating struct sr_config
Use new struct sr_config_info for option metadata
Deprecate SR_HWOPT_MODEL

This was only ever used for the defunct genericdmm driver.
Adjust session debugging to the new SR_DF_META packets.
No need to send a metapacket when loading a sigrok file.
Unify all SR_HWOPT_* and SR_HWCAP_* enums.

Only two functions remain for accessing meta info on the keys:
sr_config_info_get() and sr_config_info_name_get().
Rename SR_HWOPT_* and SR_HWCAP_* to SR_CONF_*
uni-t-dmm: use new sr_config struct
Header cleanup: remove unused structs.
serial: more serial processing flags to turn off