libplist: Update to version 2.4.0

libplist: Update to version 2.4.0

- Update from version 2.3.0 to 2.4.0
- Update of rootfile
- Changelog
    2.4.0
	- Changes:
	  * Add a PLIST_OPT_NONE value to plist_write_options_t
	  * autoconf: Allow disabling build of test suite
	  * Update doxygen config and document undocumented macros
	  * Add an explicit PLIST_FORMAT_NONE value
	  * Add a libplist_version() function to the interface
	  * docs: Use README.md to generate mainpage with doxygen
	- Bugfixes:
	  * Several compiler-related fixes and code improvements
	  * Plug memory leak in plist_write_to_stream()
	  * Prevent adding NULL items to array/dictionary nodes
	  * Fix parallel running of test suite
	  * Fix cython bindings
	  * Fix OOB read in plist_from_memory()

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