Add static_cast<int> in HPositionInfo::position to please Win64 build.

Improvements in positions handling in optimizing compiler.

- When building binary arithmetic op and comparison restore source position of the operation itself before building operation itself after it was changed by building operands. This ensures that position recorded for operation points to the operation token instead of pointing to the rightmost operand;

- Add support for recording operands' positions and use these positions when inserting HChange instructions;

- When generating hydrogen.cfg emit H-instruction position as BCI (previously 0 was emitted), additionally on every lithium instruction emit annotation pointing to corresponding hydrogen-instruction. This allows to easily reach from deopt_id to lithium instruction and from it to hydrogen instruction and source position.

R=danno@chromium.org

Review URL: https://codereview.chromium.org/59703011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17848 ce2b1a6d-e550-0410-aec6-3dcde31c8c00