Fix for issue #282

The fix limits recursion depths when parsing arrays and objects.
The limit is configurable via the `JSON_PARSER_MAX_DEPTH` setting
within `jansson_config.h` and is set by default to 2048.

Update the RFC conformance document to note the limit; the RFC
allows limits to be set by the implementation so nothing has
actually changed w.r.t. conformance state.

Reported by Gustavo Grieco.

android/jansson_config.h

@@ -36,4 +36,8 @@
    otherwise to 0. */
 #define JSON_HAVE_LOCALECONV 0
 
+/* Maximum recursion depth for parsing JSON input.
+   This limits the depth of e.g. array-within-array constructions. */
+#define JSON_PARSER_MAX_DEPTH 2048
+
 #endif