io: add r5js.R5RSCompliantOutputPort.
repl: jqconsole should use a R5RSCompliantOutputPort.
repl+ui: improve structure of jqconsole repl.
Revert "Makefile: lint all files on pre-commit, not just staged ones."

Linting the whole codebase significantly slows down development.

This reverts commit 5754168de8598deacc5621bd5a0fb7b0f3bb00a8.
test: matchers/evaluates_to.js: insert casts to quiet new compiler errors.
eval+repl: add new r5js.Repl interface + impl. Don't use yet.