Merge from origin/emacs-26

Merge from origin/emacs-26

79108894db Port to IBM xlc 12.01
d14956099d Simplify by removing HAVE_STRUCT_ATTRIBUTE_ALIGNED
b1573a97e1 Use alignas to fix GCALIGN-related bugs
5d68dc9a2f Change vectorlike from struct to union
6aa0a26b46 Don't enable cursor-sensor-mode in mhtml-mode
2b8ef8dddf * lisp/files.el (abbreviate-file-name): Doc fix.  (Bug#29267)
fe85ce1e16 Unbreak interactive run of a flymake test (bug#29267)
48ad00390d Fix Bug#29225
42daf83f08 CC Mode: Fix defun-open being recognized as brace-list-ope...
7775c47298 Merge from Gnulib
e470d16448 Pacify GCC when configured --with-x-toolkit=no
49450d0951 * lisp/find-dired.el (find-grep-dired): Doc fix.  (Bug#29262)
e286b3381f Fix more flymake-diag-region eob corner cases and add test...

# Conflicts:
#	src/lisp.h