Geometry::create_from_json used strings as things that reinitialize
the je (json_engine). By reinitializing with json_start the killed
pointer gets reset, and also the concept of depth is reset.

There are two states in create_from_json:
1. The search if for the type, once found ci is set
2. Search for the argument, arg becomes != T_NONE

If the type is found first, ci become the class, and once
the arg is found, continued execution on the same je occurs.

If the argument comes before the "type", we've save a copy
of the json_engine_t to process this argument.

In both cases je after the execution is the most progressed
pointer.

Debug assertions on je state aren't enforced by code, if
some invalid GeoJSON is passed, these are actual errors.

Because Geometry::create_from_json is recursive, from
geometrymcollections, a json_read_value is pushed from inside this
function up to Item_func_geometry_from_json::val_str.

Other Gis*::init_from_json start from their actual object and don't
need a json_read_value to start.

Test case an bug report thanks to byteoverride.