Unify handling of position info in AST, part 2

* Eliminate Conditional::then/else_position and WhileStatement::condition_position.

R=yangguo@chromium.org
BUG=

Review URL: https://codereview.chromium.org/23597037

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17184 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Use pages from lower to higher addresses in new space.

This CL constitutes the invariant that the top pointer in new space is always larger than objects allocated since the last new space garbage collection.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/26865004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17185 ce2b1a6d-e550-0410-aec6-3dcde31c8c00