Json daccor

json daccor is a json-schema validation library that accepts json-c
objects as input, and seems to be designed for openwrt, a system
with very similar requirements to BMCs.

Using this library has several motivations.  First, it keeps
libcper as a C application so integrations aren't required to provide
a c++ toolchain to be able to run unit tests.
Next, it means that we avoid an "expensive" conversion in unit tests
from json-c -> nlohmann just so we can use a third library, valijson
In terms of dependency count, it drops one dependency.
(nlohmann+valijson) to (json daccor)
Finally, it means that in the future versions of the library, we
can allow json-schema verification as an option in the library
itself, which would allow us to give a CLI option for verifying
schema on any arbitrary output (helping in debugging).

Testing to see if it will work and what improvements it makes

Change-Id: I1c00bf2ef9b898b2e5decd90b749c784fb4de109
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/meson.build b/meson.build
index a946d11..e669bb8 100644
--- a/meson.build
+++ b/meson.build
@@ -73,15 +73,7 @@
 
 cc = meson.get_compiler('c')
 
-json_c_dep = dependency('json-c', required: false)
-if not json_c_dep.found()
-    json_c = subproject(
-        'json-c',
-        required: true,
-        default_options: ['warning_level=0'],
-    )
-    json_c_dep = json_c.get_variable('json_c_dep')
-endif
+json_c_dep = dependency('json-c')
 
 libcper_include = ['include']
 libcper_include_dir = include_directories(libcper_include, is_system: true)