Make json_error_t transparent again

After looking at the new code for a few days, I didn't like it
anymore. To prepare for the future, a few fields will be added to the
json_error_t struct later.

This reverts commit 23dd078c8d. Some
adjustments were needed because of newer commits.

test/bin/json_process.c

@@ -31,7 +31,7 @@ int main(int argc, char *argv[])
     size_t flags = 0;
 
     json_t *json;
-    json_error_t *error;
+    json_error_t error;
 
     if(argc != 1) {
         fprintf(stderr, "usage: %s\n", argv[0]);
@@ -61,10 +61,7 @@ int main(int argc, char *argv[])
 
     json = json_loadf(stdin, 0, &error);
     if(!json) {
-        fprintf(stderr, "%d\n%s\n",
-                json_error_line(error),
-                json_error_msg(error));
-        free(error);
+        fprintf(stderr, "%d\n%s\n", error.line, error.text);
         return 1;
     }
 

test/suites/api/check-exports

@@ -47,8 +47,6 @@ json_object_iter_set_new
 json_dumps
 json_dumpf
 json_dump_file
-json_error_line
-json_error_msg
 json_loads
 json_loadf
 json_load_file

test/suites/api/test_load.c

@@ -12,16 +12,13 @@
 int main()
 {
     json_t *json;
-    json_error_t *error;
+    json_error_t error;
 
     json = json_load_file("/path/to/nonexistent/file.json", 0, &error);
-    if(json)
-      fail("json_load didn't return an error!");
-    if(json_error_line(error) != -1)
+    if(error.line != -1)
         fail("json_load_file returned an invalid line number");
-    if(strcmp(json_error_msg(error), "unable to open /path/to/nonexistent/file.json: No such file or directory") != 0)
+    if(strcmp(error.text, "unable to open /path/to/nonexistent/file.json: No such file or directory") != 0)
         fail("json_load_file returned an invalid error message");
 
-    free(error);
     return 0;
 }