Multi-thread setting for Firefox

Firefox finally supports multi-thread (multi-content) for faster web browsing. The default setting is good for typical PC of ~4GB RAM. If you have bigger RAM, you can increase the number of thread by:
1. about:config
2. set browser.tabs.remote.autostart to True to enable multi-processor support

3. set "dom.ipc.processCount" to 6 or 8 to set the number of process.