qapi: fix build on glib < 2.28

The following commits:
    qapi: make string output visitor parse int list
    qapi: make string input visitor parse int list
break with glib < 2.28 since they use the
new g_list_free_full function.

Open-code that to fix build on old systems.

Cc: Hu Tao <hutao@cn.fujitsu.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

qapi/string-input-visitor.c

@@ -32,6 +32,11 @@ struct StringInputVisitor
     const char *string;
 };
 
+static void free_range(void *range, void *dummy)
+{
+    g_free(range);
+}
+
 static void parse_str(StringInputVisitor *siv, Error **errp)
 {
     char *str = (char *) siv->string;
@@ -108,8 +113,9 @@ static void parse_str(StringInputVisitor *siv, Error **errp)
 
     return;
 error:
-    g_list_free_full(siv->ranges, g_free);
-    assert(siv->ranges == NULL);
+    g_list_foreach(siv->ranges, free_range, NULL);
+    g_list_free(siv->ranges);
+    siv->ranges = NULL;
 }
 
 static void
@@ -314,7 +320,8 @@ Visitor *string_input_get_visitor(StringInputVisitor *v)
 
 void string_input_visitor_cleanup(StringInputVisitor *v)
 {
-    g_list_free_full(v->ranges, g_free);
+    g_list_foreach(v->ranges, free_range, NULL);
+    g_list_free(v->ranges);
     g_free(v);
 }
 

qapi/string-output-visitor.c

@@ -316,13 +316,19 @@ Visitor *string_output_get_visitor(StringOutputVisitor *sov)
     return &sov->visitor;
 }
 
+static void free_range(void *range, void *dummy)
+{
+    g_free(range);
+}
+
 void string_output_visitor_cleanup(StringOutputVisitor *sov)
 {
     if (sov->string) {
         g_string_free(sov->string, true);
     }
 
-    g_list_free_full(sov->ranges, g_free);
+    g_list_foreach(sov->ranges, free_range, NULL);
+    g_list_free(sov->ranges);
     g_free(sov);
 }