Patch to enhance the source code line information for profiler.

This patch is to enhance the source code line information for profiler.

For the Hydrogen compilation, most of the source code line information
is not copied from the HInstruction the to corresponding LInstruction.

This patch defines one PositionBits field for LInstruction and copies the
sorce code position value from the HInstruction.

When Generating the native code, we use RecordPosition(..) function to
write LInstruction's position value to position recorder.

For the MIPS platform, I did not touch because I have no devices
to verify the modification on it.

R=danno@chromium.org

Review URL: https://codereview.chromium.org/21042003

Patch from Chunyang Dai <chunyang.dai@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16114 ce2b1a6d-e550-0410-aec6-3dcde31c8c00