qstring: add qstring_get_length()

Long overdue.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>

qobject/qstring.c

@@ -31,6 +31,14 @@ QString *qstring_new(void)
     return qstring_from_str("");
 }
 
+/**
+ * qstring_get_length(): Get the length of a QString
+ */
+size_t qstring_get_length(const QString *qstring)
+{
+    return qstring->length;
+}
+
 /**
  * qstring_from_substr(): Create a new QString from a C string substring
  *