* `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).
* If fails, exit with error message, eg: `Yang error: Sanity check failed: LIST vsDataContainer lacks key statement which MUST be present (See RFC 7950 Sec 7.8.2)`
* Can be disabled by setting `CLICON_CLICON_YANG_LIST_CHECK` to `false`
threshold of quadratic and linear growth of CLIgen buffers (cbuf:s)
* Memory footprint
* Do not autopopulate namespace cache, instead use on-demand, see `xml2ns()`.
* Set CBUF start level to 256 (`CLICON_CLI_BUF_START` option)
* Reduced xml child vector default size from 4 to 1 with quadratic growoth to 64K then linear
* Yang Netconf leaf/leaf-list insert support
* For "ordered-by user" leafs and leaf-lists, the insert and value/key attributes are supported according to RFC7950 Sections 7.7.9 and 7.8.6
* Fixed RESTCONF api-path leaf-list selection was not made properly
* `201 Created` for created resources
* `204 No Content` for replaced resources.
* See [RESTCONF: HTTP return codes are not according to RFC 8040](https://github.com/clicon/clixon/issues/56)
* HTTP `Location:` fields added in RESTCONF POST replies
* Restconf RFC 8040 increased feature compliance
* Cache-Control: no-cache added in HTTP responses (RFC Section 5.5)
* Restconf monitoring capabilities (RFC Section 9.1)
* Added support for Yang extensions
* New plugin callback: ca_extension
* Main backend example includes example code on how to implement a Yang extension in a plugin.
* JSON changes
* Non-pretty-print output removed all extra spaces.
* Example: `{"nacm-example:x": 42}` --> {"nacm-example:x":42}`
* Empty JSON container changed from `null` to `{}`.
* Empty list and leafs remain as `null`
* Removed unnecessary configure dependencies
* libnsl, libcrypt, libm, if_vlan,...
* pseudo-plugin added, to enable callbacks also for main programs. Useful for extensions
* Yang Unique statements with multiple schema identifiers did not work on some platforms due to memory error.
