Fix Wbitwise-instead-of-logical warnings

`a || b` only evaluates b if a is false. `a | b` always evaluates
both a and b. If a and b are of type bool, || is usually what you
want, so clang now warns on `|` where both arguments are of type bool.

This warning fires twice in harfbuzz. In both cases, `|` is used
intentionally, with a comment explaining this.

Slightly reorder the code a bit to make the compiler happy, and to
make it obvious even without a comment that both calls should be evaluated.

No intended behavior change.