Now it uses the window id to identify the REPL window. It is stored in
the option x11_repl_id. That way it is possible to have different REPLs
for different buffers or windows.
It's unclear what the `send-text` alias does at first glance,
so prefixing it with "repl-" both fixes that and helps make it
discoverable via the command prompt's fuzzy matcher.
The `repl` alias also seems too generic a name, the "-new" suffix
should hopefully give a hint that it creates a new window.
This commit removes attempts to auto-detect the version of the local
Tmux binary.
The Tmux package that ships with OpenBSD doesn't have a version
number[1], and therefore doesn't provide any way to check if it's
compatible with the REPL module, making the feature disabled by
default in that distribution.
Fixes#3237.
[1] https://github.com/tmux/tmux/issues/1141#issuecomment-340244302
