Emacs should no longer unexpectedly alter the byte order mark

Emacs should no longer unexpectedly alter the byte order mark

This upstream patch has been incorporated to fix the problem:

  Better support utf-8-with-signature and utf-8-hfs in XML/HTML

  * lisp/international/mule.el (sgml-xml-auto-coding-function):
  Support UTF-8 with BOM and utf-8-hfs as variants of UTF-8, and
  obey the buffer's encoding if it is one of these variants, instead
  of re-encoding in UTF-8 proper.  (Bug#20623)

Origin: backport, commit: 889f07c352f7e0deccf59353a60a45f2716551d8)
Bug: https://bugs.gnu.org/20623
Bug-Debian: http://bugs.debian.org/883434
Forwarded: not-needed