fix static-analyzer logging/CHECK macros

Two small changes in one:

- `foo || for (;;abort()) bar();` isn't valid C or C++, since for is a
  statement. We need an expression instead.
- we'll now treat everything after LOG(foo) as unreachable in the
  static analyzer, as long as we can prove at compile-time that
  foo == FATAL.

The impact of this, running across internal master, is that we see ~50
fewer medium/high-severity false positives from clang-tidy. We see 15
new complaints about unreachable code (at the "tidy" severity), but all
of them are harmless AFAICT (e.g.

switch (foo) {
  // ...
  default:
    LOG(FATAL) << "Unhandled case!"; // or CHECK(false);
    break; // clang-tidy: unreachable break.
})

(Some of the macros were forcibly formatted by the clang-format hook)

Bug: None
Test: Ran
`DEFAULT_GLOBAL_TIDY_CHECKS=clang-analyzer*,-clang-analyzer-alpha* m`;
stared at warn.py output.

Change-Id: Ie984eda0481afad4274b9def7c61ba777cfa289a