tools: require at least json-c 0.15

If not available, fallback to using YAJL.

The code is using json_c_visit() which was introduced in 0.13.
json_object_new_null() and json_object_new_uint64() where added to
0.14. And the last one json_object_new_array_ext() was introduced in
0.15.

Signed-off-by: Anthony PERARD <anthony.perard@vates.tech>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>

README

@@ -53,7 +53,8 @@ provided by your OS distributor:
     * Development install of Python 2.7 or later (e.g., python-dev)
     * Development install of curses (e.g., libncurses-dev)
     * Development install of uuid (e.g. uuid-dev)
-    * Development install of json-c (e.g. libjson-c-dev) or yajl (e.g. libyajl-dev)
+    * Development install of json-c 0.15 or later (e.g. libjson-c-dev)
+      or yajl (e.g. libyajl-dev)
     * Development install of libaio (e.g. libaio-dev) version 0.3.107 or
       greater.
     * Development install of GLib v2.0 (e.g. libglib2.0-dev)