* RFC 8528 yang schema mount-points:
* Made expand_dbvar and cli_dbxml mountpoint-aware (RFC 8528)
* autocli supportgenerate
* Made api_path2xml and xml2api_path mount-point-aware
* Temporar fix in clixon_custom.h: XPATH_CANONICAL_SKIP_CHECK
* `xml2xpath()`: Added `apostrophe` as 4th parameter, default 0
* removed extra assert.h includes
* Added flag names: `CLIXON_DBG_*`
* Added maskable flags that can be combined when debugging:
* `DEFAULT` = 1: Basic debug message, espcially initialization
* `MSG` = 2: Input and output packets, read datastore
* `DETAIL` = 4: Details: message dump in hex, xpath parse trees, etc
* `EXTRA` = 8: Extra detailed logs
* Test: some errors in yang-lib where content-id was in wrong place
* Some complexities in Section 3.7 Lexical Structure of XPath 1.0 spec
* There used to be some cornercases where function-names could not be used as nodes
* For example, `node()` is a nodetest, so `/node/` caused an error.
* In the grammar these include: axisnames, nodetests, functionnames
* The NCNames vs functionnames is now impölemented according to the lexical structure section
Fixed cornercase of restconf error return when no body
Fixed cornercase when exactly / given as xpath
Better error message when YANG not found: added which YANG file imports it
* Fixed: [Performance issue when parsing large JSON param](https://github.com/clicon/clixon/issues/266)
* Moved strlen() from for end condition
* Fixed debugging of xpath parser
* Example: `GET restconf/data/x:a=`
* Previous meaning (wrong): Return all `a` elements.
* New meaning (correct): Return the `a` instance with empty key string: "".
* [RESTCONF GET request of single-key list with empty string returns all elements #213](https://github.com/clicon/clixon/issues/213)
* [RESTCONF GETof lists with empty string keys does not work #214](https://github.com/clicon/clixon/issues/214)
* `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).
