Include the json-c.lib, .pdb and .exp files in the zip file created by the appveyor build, since it seems they're needed for linking and debugging.

appveyor.yml

@@ -32,7 +32,7 @@ after_build:
 - copy json_inttypes.h include\json-c\*
 - copy include\json_config.h include\json-c\*
 - copy json_object_private.h include\json-c\*
-- 7z a json-c.lib.zip lib\json-c.dll include\json-c\*.h
+- 7z a json-c.lib.zip lib\json-c.dll Debug\json-c.lib Debug\json-c.exp Debug\json-c.pdb include\json-c\*.h
 
 artifacts:
 - path: json-c.lib.zip