不能安装！！为什么，原来是有个3.8的网站不在available范围内，去google找到了答案：
Q:eclipsercp.org问题---->深入浅出rcp
1. Help->Install New Software...
2. Click Available Update sites link
3. Add http://download.eclipse.org/eclipse/updates/3.8
(extracted from https://wiki.eclipse.org/Eclipse_Project_Update_Sites)
but install nothing
4. Go back to install and Add http://eclipsercp.org
5. Check if not checked Contact all update sites...
6. Select all and install