replace "Mac OS X" with "macOS"

except in older release notes where the name was actually Mac OS X.

doc/manual/command-ref/conf-file.xml

@@ -262,7 +262,7 @@ false</literal>.</para>
     system (except that fixed-output derivations do not run in private
     network namespace to ensure they can access the network).</para>
 
-    <para>Currently, sandboxing only work on Linux and Mac OS X. The use
+    <para>Currently, sandboxing only work on Linux and macOS. The use
     of a sandbox requires that Nix is run as root (so you should use
     the <link linkend='conf-build-users-group'>“build users”
     feature</link> to perform the actual builds under different users

doc/manual/installation/installing-binary.xml

@@ -6,7 +6,7 @@
 
 <title>Installing a Binary Distribution</title>
 
-<para>If you are using Linux or Mac OS X, the easiest way to install
+<para>If you are using Linux or macOS, the easiest way to install
 Nix is to run the following command:
 
 <screen>
@@ -39,7 +39,7 @@ behaviour.
 <!--
 <para>You can also manually download and install a binary package.
 Binary packages of the latest stable release are available for Fedora,
-Debian, Ubuntu, Mac OS X and various other systems from the <link
+Debian, Ubuntu, macOS and various other systems from the <link
 xlink:href="http://nixos.org/nix/download.html">Nix homepage</link>.
 You can also get builds of the latest development release from our
 <link

doc/manual/installation/multi-user.xml

@@ -52,7 +52,7 @@ This creates 10 build users. There can never be more concurrent builds
 than the number of build users, so you may want to increase this if
 you expect to do many builds at the same time.</para>
 
-<para>On Mac OS X, you can create the required group and users by
+<para>On macOS, you can create the required group and users by
 running the following script:
 
 <programlisting>

doc/manual/installation/supported-platforms.xml

@@ -12,7 +12,7 @@
 
   <listitem><para>Linux (i686, x86_64).</para></listitem>
 
-  <listitem><para>Mac OS X (x86_64).</para></listitem>
+  <listitem><para>macOS (x86_64).</para></listitem>
 
   <!--
   <listitem><para>FreeBSD (only tested on Intel).</para></listitem>

doc/manual/introduction/about-nix.xml

@@ -236,7 +236,7 @@ href="[%root%]hydra">a continuous build system</a>.</para>
 
 <simplesect><title>Portability</title>
 
-<para>Nix runs on Linux and Mac OS X.</para>
+<para>Nix runs on Linux and macOS.</para>
 
 </simplesect>
 

src/libutil/archive.cc

@@ -72,7 +72,7 @@ static void dump(const Path & path, Sink & sink, PathFilter & filter)
     else if (S_ISDIR(st.st_mode)) {
         sink << "type" << "directory";
 
-        /* If we're on a case-insensitive system like Mac OS X, undo
+        /* If we're on a case-insensitive system like macOS, undo
            the case hack applied by restorePath(). */
         std::map<string, string> unhacked;
         for (auto & i : readDirectory(path))