gentests: _testgen/gentest.go uses internal import from aqwari.net/xml

[kortschak]

When I attempt to follow the instructions in the README.md I get the following.

~/src/github.com/droyo/go-xml/gentests [master]$ go generate
_testgen/testgen.go:14:2: use of internal package aqwari.net/xml/internal/gen not allowed
gentest.go:5: running "go": exit status 1
~/src/github.com/droyo/go-xml/gentests [master]$ git rev-parse HEAD
d48ea63e5a613b3e7b7360e2d0f3476ea77c263d

From following the godoc, it appears that this is because this package is in fact aqwari.net/xml, though this isn't noted in the README here, and there is no import comment restricting incorrect imports.