libyang: Update to version 3.7.8

libyang: Update to version 3.7.8

- Update from version 2.1.148 to 3.7.8
- Update of rootfile
- Submited as a set with a PAK_VER update of frr as frr needs to be shipped to use this
   new version.
- In the changelog for moving the library from 2.x to 3.0 it mentions that there are
   some breaking changes but then says they are minor. The library versions are not
   alligned with the package version numbers.
   Following is what is said:-
     * Non-backwards-compatible changes between libyang version 2 and 3 are rather
       minor and can be summarized as providing
	* structured error information (instead of a single message), unifying
	  **lyd_new_*()** function options, and some
	* minor changes such as removing deprecated functions or making a few functions
	  inlined. However, there is another
	* large change that has not affected the API, specifically configuration
	  system-ordered lists and leaf-lists are now
	* ordered based on their keys/values, respectively. Except for moderately
	  slower performance and negligible increased
	* memory requirements, it should not affect existing applications (assuming
	  they do not rely on the previous order of
	* these instances).
- I tested this updated version of libyang with frr. frr built without any problems. It
   just has the requirement that libyang >= 2.1.128, so no restriction that it must not
   be version 3. I then installed the IPFire built with the updated libyang and installed
   the frr that was built with it. I was able to start frr successfully, so all the
   specified frr daemons successfully started.
- I could only test that frr successfully had all the daemons start but could not test
   out actual functioning of frr as this is something I have never used. I would expect
   that if all the daemons start successfully then frr should be happy working with
   libyang-3.7.8
- Changelog
    3.7.8
	    yanglint UTF8 support
	    validation optimizations
	    lots of bugfixes
    3.4.2
	    data handling optimizations
	    32b build fixes
	    various bugfixes
    3.1.0
	    lots of improvements and bugfixes in various parts of the library
    2.2.8
	    new SO version 3
	        with some non-backwards compatible changes
	        transition manual from version 2 in docs
	    (leaf-)list instance semantic ordering
	        sorts instances based on their values or their key values
	        minor performance cost
	    logging API improved
	    new parsing flag LYD_PARSE_STORE_ONLY
	        avoids value validation
	    run-time plugin support
	    build improvements
	    lots of other bugfixes and optimizations

Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>