Merge from origin/emacs-26

Merge from origin/emacs-26

7e7f2ea (origin/emacs-26) * src/keyboard.c (syms_of_keyboard): Doc fi...
c0676d4 Improve documentation of X resources
d806d69 ; Use @minus for negative numbers in some texi files
4a8ea7d * lisp/international/mule.el (keyboard-coding-system): Doc fix.
8a73b80 Minor doc fixes, mostly for timestamp issues
361a8b9 * doc/emacs/mini.texi (Completion Styles): Improve indexing.
2dc24d5 Fix @findex and @vindex entries in manuals
76f5242 Document, in the Elisp manual, how to get a character's raw s...
5fb2957 Improvements in the Emacs manual
de17b8e Tiny doc/misc markup fixes