Fix outdated header guard names

One of these lint errors is blocking a CL that moves optional.h to
webrtc/api/. And while I made a CL to fix that one, I figured I might
as well fix them all.

BUG=webrtc:8205

Review-Url: https://codereview.webrtc.org/3008143002
Cr-Original-Commit-Position: refs/heads/master@{#19692}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: ad43d4b29e54a914eeb88e7bc26db2271c5742f5
5 files changed