Merge from origin/emacs-26

Merge from origin/emacs-26

bc8dc37 (origin/emacs-26) Minor copyedits in "Distribution" chapter o...
1c7a936 Minor copyedits in "Entering" chapter of Emacs manual.
1d4498b Minor wording change in the Emacs manual
2bf49e7 Fix a typo in the Emacs manual
f3546a2 Improve the "Basic" chapter of the Emacs manual
691431e Resurrect lost text in lispref
956807b * lisp/emacs-lisp/rx.el (rx): Fix the definition of 'blank'.
7d90d2e Proofread os.texi and files.texi
490c736 Minor improvements in the "International" chapter of Emacs ma...
79252d3 Minor improvement in "Text" chapter of Emacs manual