lang/janet: Update to 1.27.0

## 1.27.0 - 2023-03-05

- Change semantics around bracket tuples to no longer be equal to regular
  tuples.
- Add `index` argument to `ffi/write` for symmetry with `ffi/read`.
- Add `buffer/push-at`
- Add `ffi/pointer-buffer` to convert pointers to buffers the cannot be
  reallocated. This allows easier manipulation of FFI memory, memory mapped
  files, and buffer memory shared between threads.
- Calling `ev/cancel` on a fiber waiting on `ev/gather` will correctly cancel
  the child fibers.
- Add `(sandbox ...)` function to core for permission based security. Also add
  `janet_sandbox` to C API.  The sandbox allows limiting access to the file
  system, network, ffi, and OS resources at runtime.
- Add `(.locals)` function to debugger to see currently bound local symbols.
- Track symbol -> slot mapping so debugger can get symbolic information.  This
  exposes local bindings in `debug/stack` and `disasm`.
- Add `os/compiler` to detect what host compiler was used to compile the
  interpreter
- Add support for mingw and cygwin builds (mingw support also added in jpm).

(charlotte)