v0.16.5

Move the sigil-lib and sigil-test dev-dependency pins from ^0.17 to ^0.19.

The ^0.17 pin carried a documented reason: sigil-crypto's native codegen was said to need the 0.17 runtime headers to build libsigil-crypto.a. That reason has expired, and measurement shows it had inverted.

Two arms on a 0.19.2 host, isolated trees:

  ^0.17   libsigil-crypto.a builds (5891408 B), tests FAIL
          "unsupported bytecode version 11 (expected 10)"
  ^0.19   libsigil-crypto.a builds (5891528 B), tests 100/100 PASS

So the pin does not protect the native codegen. It is what breaks sigil test on a 0.19 host. The library builds either way.

Why this is a patch and not a minor: it raises a toolchain floor, which looks like a compatibility change. Every consumer it would break is already broken, because on a 0.19 host the old pin is what makes the test suite fail. This removes a defect rather than changing an API.

sigil-crypto is one of only two extracted packages that declare sigil-lib (the other is sigil-tls), which makes these two the origin of every stale sigil-lib ^0.17 row in the estate.