Add missing `static` for macOS inline.

Also switch to #pragma once and s/__inline__/inline/g for consistency.

There are a handful of inlines that are missing static, which seems like
a bug, but I've left those for now.

Bug: http://b/153328340
Test: treehugger
Change-Id: I2353215c0a8a6154ce8b39ecde022b282f5c0cb9