base: Prettier JSON output / options

- Add flags for indenting with 2, 4, or 8 spaces, still defaulting to
   tabs if none of those are set.

 - Don't emit a newline before emitting scalar values in dicts.

lib/base/heimbase.h

@@ -463,7 +463,11 @@ typedef enum heim_json_flags {
 	HEIM_JSON_F_STRICT = 31,
 	HEIM_JSON_F_CNULL2JSNULL = 32,
 	HEIM_JSON_F_TRY_DECODE_DATA = 64,
-	HEIM_JSON_F_ONE_LINE = 128
+	HEIM_JSON_F_ONE_LINE = 128,
+        /* The default is to indent with one tab */
+	HEIM_JSON_F_INDENT2 = 256,
+	HEIM_JSON_F_INDENT4 = 512,
+	HEIM_JSON_F_INDENT8 = 1024,
 } heim_json_flags_t;
 
 heim_object_t heim_json_create(const char *, size_t, heim_json_flags_t,