Move MinPositive to call.h as discussed here: https://codereview.chromium.org/2888303005/#msg19

TBR=stefan@webrtc.org
BUG=webrtc:7395

Review-Url: https://codereview.webrtc.org/2924393002
Cr-Original-Commit-Position: refs/heads/master@{#18599}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: a5e0df643828c1d16ce3b508849d0c4ed6130081
5 files changed