Move pure+side-effect-free declarations to byte-opt.el

* src/json.c (syms_of_json): Move pure and side-effect-free declarations
for json-serialize and json-parse-string from here...
* lisp/emacs-lisp/byte-opt.el (side-effect-free-fns, pure-fns):
...to here.

lisp/emacs-lisp/byte-opt.el

@@ -1789,6 +1789,8 @@ See Info node `(elisp) Integer Basics'."
          tool-bar-pixel-width window-system
          ;; fringe.c
          fringe-bitmaps-at-pos
+         ;; json.c
+         json-serialize json-parse-string
          ;; keyboard.c
          posn-at-point posn-at-x-y
          ;; keymap.c
@@ -1979,6 +1981,8 @@ See Info node `(elisp) Integer Basics'."
          length> member memq memql nth nthcdr proper-list-p rassoc rassq
          safe-length string-bytes string-distance string-equal string-lessp
          string-search string-version-lessp take value<
+         ;; json.c
+         json-serialize json-parse-string
          ;; search.c
          regexp-quote
          ;; syntax.c

src/json.c

@@ -1818,16 +1818,6 @@ syms_of_json (void)
   define_error (Qjson_escape_sequence_error,
 		"invalid escape sequence", Qjson_parse_error);
 
-  DEFSYM (Qpure, "pure");
-  DEFSYM (Qside_effect_free, "side-effect-free");
-
-  DEFSYM (Qjson_serialize, "json-serialize");
-  DEFSYM (Qjson_parse_string, "json-parse-string");
-  Fput (Qjson_serialize, Qpure, Qt);
-  Fput (Qjson_serialize, Qside_effect_free, Qt);
-  Fput (Qjson_parse_string, Qpure, Qt);
-  Fput (Qjson_parse_string, Qside_effect_free, Qt);
-
   DEFSYM (QCobject_type, ":object-type");
   DEFSYM (QCarray_type, ":array-type");
   DEFSYM (QCnull_object, ":null-object");