* New clixon-lib@2020-12-30.yang revision
* Added callback to process-control RPC feature in clixon-lib.yang to manage processes
* Changed behavior of starting restconf internally using `CLICON_BACKEND_RESTCONF_PROCESS` monitoring changes in enable flag, not only the RPC.
* Changed: RPC process-control output parameter status to pid
* This is an alternative to manage a clixon daemon via sudtemd, containerd or other
* One important special case is starting the clixon-restconf daemon internally
* This is how it works:
* Register a process via `clixon_process_register(h, name, namespace, argv, argc)`
* Use process-control RPC defined in clixon-lib.yang to start/stop/restart or query status on that process
* Example code in the main example
* The existing autocli does not support modes, complete paths must be given, eg: `set a b c d 42`.
* In the new auto-cli, automatic modes are present at each YANG syntax node level, eg the above can be given as: `edit a b c; set d 4; top`
* The existing CLI API remains, the new API is as follows: `cli_auto_edit()`, `cli_auto_up()`, `cli_auto_top()`, `cli_auto_show()`, `cli_auto_set()`, `cli_auto_merge()`, `cli_auto_create()`, `cli_auto_del()`.
* See `test/test_cli_auto.sh` for an example of the new API, and `apps/cli/cli_auto.c` for the source code of the new callback API.
* Documentation will be appear and full integration with the main example.
* Added inline state field to clixon-example.yang
* Added new clicon_data_cvec_*() API for generic cvec structs
* `count`, `name`, `contains`, `not`, as defined in [xpath 1.0](https://www.w3.org/TR/xpath-10)
* `deref`, `derived-from` and `derived-from-or-self` from RFC7950 Section 10.
* in particular in augment/when statements
* Improved error handling
* Verification of XPath functions is done at startup when yang modules are loaded, not when XPaths are evaluated.
* Separation of "not found" and "not implemented" XPath functions
* Both give a fatal error (backend does not start).
* Only requests on the form: `<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"><edit-config>...` will be accepted
* All replies will be on the form: `<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">...`
* Requests such as: `<rpc><edit-config>...` will not be accepted.
* You can revert this behaviour (to clixon pre-4.6 behaviour) by enabling `CLICON_NAMESPACE_NETCONF_DEFAULT`
* This API change is a consequence of: [copy-config's RPC cxobj parameter does not contain namespace #131](https://github.com/clicon/clixon/issues/131)
* Enforcing RFC 7950 Sec 7.6.1 means unassigned top-level leafs (or leafs under non-presence containers) are assigned default values.
* NACM default behaviour is read-only (empty configs are dead-lockedd)
* This applies if NACM is loaded and `CLICON_NACM_MODE` is `internal`
* Fixed: [default values don't show up in datastores #111](https://github.com/clicon/clixon/issues/111)
* Changed commit lock error tag from "lock denied" to "in-use".
* Changed unlock error message from "lock is already held" to #lock not active" or "lock held by other session".
* Fixed [lock candidate succeeded even though it is modified #110](https://github.com/clicon/clixon/issues/110)
1. Added #ifdef extern "C" to public header files.
2. Changed variables that are key words in c++, to different names (like ns instead of namespace).
3. Add a test_c++.sh for c++ compiling.
