Add json-c dependency

Summary:
Old API retired => use yahoo weather JSON API

The new API is returning data in JSON format.
This commit is switching it over (currently SSL server) and parsing
to have the data in par with previous data.

Example data:
https://www.yahoo.com/news/_tdnews/api/resource/WeatherService;woeids=839722

Fix millibar to inches of mercury divider

Merge branch 'json-api'

Reviewers: vtorri, bu5hm4n, stephenmhouston, raster

Reviewed By: vtorri

Subscribers: raster, vtorri

Differential Revision: https://phab.enlightenment.org/D8095

src/e_mod_main.c

@@ -933,7 +933,7 @@ _forecasts_popup_content_create(Instance *inst)
 
    if (!inst->location) return;
 
-   inst->popup = e_gadcon_popup_new(inst->gcc, E_COMP_OBJECT_TYPE_POPUP);
+   inst->popup = e_gadcon_popup_new(inst->gcc, 0);
 
    evas = e_comp->evas;
    o = e_widget_list_add(evas, 0, 0);