plan9/client: make Read return quickly (#116)

Satisfy requirement of https://pkg.go.dev/io#Reader:

Read conventionally returns what is available instead of waiting for more.

Fixes #115.

draw/memdraw: fix two print formats

merge github.com/fhs/9fans-go plan9 branch

Fixes #28.

acme/Watch: send SIGINT/SIGTERM before SIGKILL when restarting program

Using SIGINT/SIGTERM avoids child processes to stay running in the background.
This is specially relevant when running programs like servers, which
have to be terminated explicitly. If they are not killed, processes
would be leaked or successive runs could fail due to unreleased
resources (e.g. network ports).

acme/Watch: send SIGINT/SIGTERM before SIGKILL when restarting program

Using SIGINT/SIGTERM avoids child processes to stay running in the background.
This is specially relevant when running programs like servers, which
have to be terminated explicitly. If they are not killed, processes
would be leaked or successive runs could fail due to unreleased
resources (e.g. network ports).

plan9/client: fix Dirreadall

plan9/client: fix Dirreadall

acme: document Show

acme/Dict: split into its own module

acme/Dict: remove replace in go.mod

Also update go.sum.