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.

1 files changed, 2 insertions, 3 deletions

diff --git a/README b/README
index 35a31dbd31e..d227ec59cc7 100644
--- a/README
+++ b/README
@@ -86,9 +86,8 @@ There are several subdirectories:
                 in Emacs Lisp manual.
 'msdos'     holds configuration files for compiling Emacs under MS-DOS.
 'nextstep'  holds instructions and some other files for compiling the
-            Nextstep port of Emacs, for GNUstep and Mac OS X Cocoa.
-'nt'        holds various command files and documentation files that pertain
-            to building and running Emacs on Windows 9X/ME/NT/2000/XP.
+            Nextstep port of Emacs, for GNUstep and macOS Cocoa.
+'nt'        holds code and documentation for building Emacs on MS-Windows.
 'test'      holds tests for various aspects of Emacs's functionality.
 
    Building Emacs on non-Posix platforms requires tools that aren't part