[automerger skipped] DO NOT MERGE: [libc++] Add `__truncating_cast` for safely casting float types to integers am: 55b6136b3a am: 9546d85a3d am: c3a80bd37a -s ours
am: f126b4ea11 -s ours
am skip reason: subject contains skip directive

Change-Id: Ie7823dcce173a2171e36f818d97b76aa29a39629