[automerger skipped] DO NOT MERGE: [libc++] Move __clamp_to_integral to <cmath>, and harden against min()/max() macros am: 7af7a63c2e am: d190f65c64 am: f0f107c222 -s ours
am: b3d336063c -s ours
am skip reason: subject contains skip directive

Change-Id: I0e7df6c385fc603eeac5febb4d703b0fecb22c99