REPL should support compat mode

[ry]

# deno -V
deno 1.15.3
# deno repl --compat --unstable
Download https://deno.land/std@0.113.0/node/global.ts
Download https://deno.land/std@0.113.0/node/process.ts
Download https://deno.land/std@0.113.0/node/timers.ts
Download https://deno.land/std@0.113.0/node/_options.ts
Download https://deno.land/std@0.113.0/node/_validators.ts
Download https://deno.land/std@0.113.0/node/internal_binding/node_options.ts
Check https://deno.land/std@0.113.0/node/global.ts
Check https://deno.land/std@0.113.0/node/global.ts
Deno 1.15.3
exit using ctrl+d or close()
> require('fs')
Uncaught ReferenceError: require is not defined
    at <anonymous>:2:1

[bartlomieju]

I'm looking into it, but first we need to address #12684