Revert "encoding/xml: reject XML declaration after start of document"
This reverts commit
8a0fbd75a54c27ff2ae624ac2775bf752cdbceb4.
Reason for revert: Breaking real-world tests inside Google,
which means it probably breaks real-world tests outside Google.
One instance I have seen is a <!-- --> comment (often a copyright notice) before the procinst.
Another test checks that a canonicalizer can handle a test input that simply has procinsts mid-XML.
XML is full of contradictions, XML implementations more so. If we are going to start being picky, that probably needs to be controlled by a GODEBUG (and a proposal).
For #65691 (will reopen manually).
Change-Id: Ib52d0944b1478e71744a2a35b271fdf7e1c972ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/570175
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Russ Cox <rsc@golang.org>