json-c: Update to version 0.18

json-c: Update to version 0.18

- Update from version 0.17 to 0.18
- Update of rootfile
- Changelog
    0.18
	Deprecated and removed features:
		* Clean up pre-3.9 CMake support in CMakeLists.txt
	New features
		* Build pkg-config for msvc as well
	Significant changes and bug fixes
		* Critical fix for binary compatibility with 0.16: Move the
		  json_tokener_error_memory entry to the end of enum json_tokener_error.
		* Issue #829: attempt to detect clang-cl.exe and pass MSVC-compatile
		  command line arguments.
		* PR #831 - rename WIN32 to _WIN32
		* PR #839 - Fix gcc 5 "may be used uninitialized" failure in
		  json_pointer.c
		* PR #849 - random_seed.c: add a Coverity Scan suppression
		* Issue #854: Set error=json_tokener_error_memory in
		  json_tokener_parser_verbose() when allocating the tokener fails.
		* Issue #857: fix a few places where json_tokener should have been
		  returning json_tokener_error_memory but wasn't.
		* Handle yet another out-of-memory condition in json_tokener,
		  duplocate can return NULL.
		* Various fixes in the fuzzers
		* A few minor doc fixes

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>