Determine why match() tests don't work on old R

[MichaelChirico]

As of #83, these tests don't pass on R 3.6.3:

bit64/tests/testthat/test-highlevel64.R

Lines 7 to 8 in fa55ef2

	expect_identical(match(2:5, y), c(NA, 1:3))
	expect_identical(match(as.numeric(2:5), y), c(NA, 1:3))

No idea why at a glance. It'll require logging into an ancient Docker.

[MichaelChirico]

This is because

1. This is using base::match() which ignores attributes / no double dispatch
2. Since R 4.2.0, base uses mtfrm() to pre-transform inputs to match(), defaulting to as.character(), hence why it works on recent versions of R