Use the (D)CHECK_{EQ,NE,GT,...} macros instead of (D)CHECK with an
embedded comparison. This gives better error messages and also does the
right comparison for signed/unsigned mismatches.

This will allow us to reenable the readability/check cpplint check.

R=marja@chromium.org

Bug: v8:6837, v8:6921
Change-Id: I17cf5cbbac3d2992c3b3588cc66e8564982453b6
Reviewed-on: https://chromium-review.googlesource.com/681355Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48596}