rename to_i32 -> trunc, and add round

This plumbs through round but doesn't use it.  I want that change to be
its own CL.  It's nice to have assembler support and the name changes
even if I revert using round.

Change-Id: I6d67ec5c63546069eb7cc1c91599b599bafcda66
Reviewed-by: Mike Reed <>
Commit-Queue: Mike Klein <>
6 files changed