libubox: add boolean type support

[BastienSAH]

Create a distinguished BLOBMSG_TYPE_BOOL in order to differenciate int8 and boolean types (both still use BLOB_ATTR_INT8 as storage format).

[BastienSAH]

Ping @nbd168 @systemcrash @Alphix

[systemcrash]

Not sure how this interacts with ubus. ubus coerces u8 to bool. So bool is u8.

https://github.com/openwrt/ubus/blob/0d4bcb56f5e1386e7dc99f1ec9f3b6c9211c8ab6/cli.c#L466

Does this cause ABI breakage?

[Alphix]

I think this might intersect with #28; so you should probably get @Noltari into the loop?

[BastienSAH]

@systemcrash: I indeed saw a regression in ubus, with the "ubus monitor" command. Some attributes like "no_reply" are now displayed as 1 instead of "true":
ubus -v monitor <- b6a665ab #9a10c460 notify: {"objid":-1710177184,..."no_reply":1}

I propose the following pull request to solve this: openwrt/ubus#25

Also, adding a boolean type indeed creates an ABI breakage, making one of the test failed (the test which parses procd-instance-nlbwmon.bin). I have added a second commit, to have backward compatibility with existing binary blobs.

[BastienSAH]

@Alphix @Noltari: do you still plan to merge #28 ? In there a boolean function was added, but I think it would be nice to have a dedicated boolean type as well.
This would be useful for prplWRT, in which the system and other buses have the boolean type.
I have made tests which are OK, for example:

• make a "ubus call" on a int8 parameter -> now the value is a real integer and not "true/false":
  ubus call WiFi.AccessPoint.1 _get -> { "WiFi.AccessPoint.1.": { "MultiAPProfile": 0,
  Before we had "MultiAPProfile": false

• make a "ubus list" -> the int8 parameters are not marked as boolean anymore:
  ubus -v list hostapd.wlan0.3 -> 'hostapd.wlan0.3' @dfae2a16 "del_client":{"addr":"String","reason":"Integer","deauth":"Int8","ban_time":"Integer"}
  Before we had "deauth":"Boolean"