Previously, `*macro-lints*` was set after the `macroexpand1` fiber was
resumed, rather than just before. And, `*macro-lints*` was never
cleared. This behavior was typically fine since the main users of
`compile` pass the same lint array repeatedly, and the first macro
expansion (somewhere in boot.janet) never produces a lint. But, when
compiling with a fresh lint array, if the first macro invocation
produced a lint, the lint was always lost.
