Merge from origin/emacs-25

0e35405 Improve documentation of coding-systems
c2fd04c Improve definition of 'variable-pitch' face on MS-Windows
16fb50d Fix an error message in python.el
a2a2073 Clarify major mode switching
fc38671 Add helpful comment to compile-command's docstring
ee65d85 Fix ':version' of 'select-enable-primary'

diff --cc doc/lispref/modes.texi
Simple merge

diff --cc doc/lispref/nonascii.texi
Simple merge

diff --cc lisp/faces.el
Simple merge

diff --cc lisp/progmodes/compile.el
Simple merge

diff --cc lisp/progmodes/python.el
Simple merge