Log Message:
janet: Update to 1.11.3

## 1.11.3 - 2020-08-03
- Add `JANET_HASHSEED` environment variable when `JANET_PRF` is enabled.
- Expose `janet_cryptorand` in C API.
- Properly initialize PRF in default janet program
- Add `index-of` to core library.
- Add `-fPIC` back to core CFLAGS (non-optional when compiling default client  \ 
with Makefile)
- Fix defaults on Windows for ARM
- Fix defaults on NetBSD.