janet: update to 1.18.1. jpm is now a separate package.

## 1.18.1 - 2021-10-16
- Fix some documentation typos
- Fix - Set pipes passed to subprocess to blocking mode.
- Fix `-r` switch in repl.

## 1.18.0 - 2021-10-10
- Allow `ev/cancel` to work on already scheduled fibers.
- Fix bugs with ev/ module.
- Add optional `base` argument to scan-number
- Add `-i` flag to janet binary to make it easier to run image files from the command line
- Remove `thread/` module.
- Add `(number ...)` pattern to peg for more efficient number parsing using Janet's
  scan-number function without immediate string creation.

## 1.17.2 - 2021-09-18
- Remove include of windows.h from janet.h. This caused issues on certain projects.
- Fix formatting in doc-format to better handle special characters in signatures.
- Fix some marshalling bugs.
- Add optional Makefile target to install jpm as well.
- Supervisor channels in threads will no longer include a wasteful copy of the fiber in every
  message across a thread.
- Allow passing a closure to `ev/thread` as well as a whole fiber.
- Allow passing a closure directly to `ev/go` to spawn fibers on the event loop.

## 1.17.1 - 2021-08-29
- Fix docstring typos
- Add `make install-jpm-git` to make jpm co-install simpler if using the Makefile.
- Fix bugs with starting ev/threads and fiber marshaling.

## 1.17.0 - 2021-08-21
- Add the `-E` flag for one-liners with the `short-fn` syntax for argument passing.
- Add support for threaded abstract types. Threaded abstract types can easily be shared between threads.
- Deprecate the `thread` library. Use threaded channels and ev instead.
- Channels can now be marshalled.
- Add the ability to close channels with `ev/chan-close` (or `:close`).
- Add threaded channels with `ev/thread-chan`.
- Add `JANET_FN` and `JANET_REG` macros to more easily define C functions that export their source mapping information.
- Add `janet_interpreter_interupt` and `janet_loop1_interrupt` to interrupt the interpreter while running.
- Add `table/clear`
- Add build option to disable the threading library without disabling all threads.
- Remove JPM from the main Janet distribution. Instead, JPM must be installed
  separately like any other package.
- Fix issue with `ev/go` when called with an initial value and supervisor.
- Add the C API functions `janet_vm_save` and `janet_vm_load` to allow
saving and restoring the entire VM state.

(nia)