Merge from origin/emacs-26

614cc65 ; * lisp/simple.el (line-move-visual): Fix typo.
d2ad4ba Do not consider external packages to be removable (Bug#27822)
ec0995c * src/alloc.c: Remove obsolete comments.
ec6f588 Better support utf-8-with-signature and utf-8-hfs in HTML
eb026a8 Don't use -Wabi compiler option

diff --cc configure.ac
Simple merge

diff --cc lisp/emacs-lisp/package.el
Simple merge

diff --cc lisp/international/mule.el
Simple merge

diff --cc lisp/simple.el
Simple merge

diff --cc src/alloc.c
Simple merge