new math.php
new question type

git-svn-id: https://plugins.svn.wordpress.org/captcha-in-thai-2nd/trunk@876908 b8457f37-d9ea-0310-8a92-e5e31aec5664
new version
fixed bug

git-svn-id: https://plugins.svn.wordpress.org/captcha-in-thai-2nd/trunk@876909 b8457f37-d9ea-0310-8a92-e5e31aec5664