This includes:

* adding the CODE_ADD_LINE_POS_INFO, CODE_START_LINE_INFO_RECORDING, CODE_END_LINE_INFO_RECORDING event and the corresponding functionality.
 * adding the JITCodeLineInfo struct to record the code line info. I added this definition because Danno mentioned that "we'd like to cleanup and decouple the external debugging functionality"
 * some other small changes.

Review URL: https://chromiumcodereview.appspot.com/12223027
Patch from Chunyang Dai <chunyang.dai@intel.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13686 ce2b1a6d-e550-0410-aec6-3dcde31c8c00