Update json-c library to version 0.11

[Mateusz Łoskot]

Release ​branch for 0.10 version of json-c library has been created in ​https://github.com/json-c/json-c

AFAIK, it will be released soon.

I have been porting local GDAL modifications applied to json-c to the upstream. I maintain GDAL-specific changes to json-c in dedicated ​gdal-modifications branch on GitHub. Some of these modifications have been accepted to upstream.

The port has been completed and I have tested it using Visual Studio 2010.

I'd like to submit update to json-c based on the pre-0.10 version to GDAL trunk, so people can start testing it. Next, I will pull this update on to Linux box continue testing there.

Any objections to submitting the new json-c to the trunk?

[Even Rouault]

Seems good to me (I assume the existing tests in ogr_geojson.py still pass on your Windows box)

[Even Rouault]

r26292 "Upgrade internal libjson-c to json-c 0.11 (#4676)"

[Even Rouault]

For Windows build, this patch is necessary (has been applied in internal copy): ​https://github.com/json-c/json-c/pull/95

[Even Rouault]

r26293 "Unix configure: add --with-libjson-c configure option to build against external libjson-c (>= 0.11) (#4676)"

[Even Rouault]

r26285 "Remove include to json_object_private.h which is unnecessary since json_object_object_foreachC is now in json_object.h"

[Even Rouault]

r26286 "Prefix symbols of internal libjson-c with gdal_ to avoid issues if an app links with GDAL and an external (older) libjsonc"

r26287 "Rename internal libjson directory from json-c to libjson to avoid include issues when linking against external libjson-c"

[Even Rouault]

Arg typo: the last 3 commits are r26294, r26295 and r26296

[Jukka Rahkonen]

Is there still something that should be done with update to json-c 0.11?