Modernize usage of 'macOS' in doc and comments

Apple changed the spelling of its operating system again, to "macOS",
effective with macOS 10.12 Sierra (2016-09-20).  Change Emacs
documentation and comments to match this.  Stick with older OS
spellings ("OS X", "Mac OS X") when talking about older releases where
the older names are more correct.

3 files changed, 3 insertions, 4 deletions

diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index f94628ce105..a49bfc8ca8c 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -6958,7 +6958,7 @@ Emacs is displaying the frame using X.
 Emacs is displaying the frame using native MS-Windows GUI.
 @item ns
 Emacs is displaying the frame using the Nextstep interface (used on
-GNUstep and Mac OS X).
+GNUstep and macOS).
 @item pc
 Emacs is displaying the frame using MS-DOS direct screen writes.
 @item nil
diff --git a/doc/lispref/nonascii.texi b/doc/lispref/nonascii.texi
index 9cf3b5750f2..e4581b3d68e 100644
--- a/doc/lispref/nonascii.texi
+++ b/doc/lispref/nonascii.texi
@@ -1034,8 +1034,7 @@ Unix convention, used on GNU and Unix systems, is to use the linefeed
 character (also called newline).  The DOS convention, used on
 MS-Windows and MS-DOS systems, is to use a carriage-return and a
 linefeed at the end of a line.  The Mac convention is to use just
-carriage-return.  (This was the convention used on the Macintosh
-system prior to OS X.)
+carriage-return.  (This was the convention used in Classic Mac OS.)
 
 @cindex base coding system
 @cindex variant coding system
diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index 0d999ae9b99..6b9b2c7faf3 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -888,7 +888,7 @@ Berkeley BSD and its variants.
 Cygwin, a Posix layer on top of MS-Windows.
 
 @item darwin
-Darwin (Mac OS X).
+Darwin (macOS).
 
 @item gnu
 The GNU system (using the GNU kernel, which consists of the HURD and Mach).