README.macOS: explain how to install suitable Texinfo

Change-Id: Ic5906111f412eebd906a9be3fd0e133484def3eb
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/6026
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

Makefile.am

@@ -48,7 +48,7 @@ EXTRA_DIST += \
 	HACKING \
 	NEWTAPS \
 	README.Windows \
-	README.OSX \
+	README.macOS \
 	$(EXTRA_DIST_NEWS) \
 	Doxyfile.in \
 	tools/logger.pl \

README.macOS

@@ -1,10 +1,10 @@
-Building OpenOCD for OSX
-------------------------
+Building OpenOCD for macOS
+--------------------------
 
 There are a few prerequisites you will need first:
 
-- Xcode 5 (install from the AppStore)
-- Command Line Tools (install from Xcode 5 -> Preferences -> Downloads)
+- Xcode (install from the AppStore)
+- Command Line Tools (install from Xcode -> Preferences -> Downloads)
 - Gentoo Prefix (http://www.gentoo.org/proj/en/gentoo-alt/prefix/bootstrap.xml)
   or
 - Homebrew (http://mxcl.github.io/homebrew/)
@@ -12,6 +12,11 @@ There are a few prerequisites you will need first:
 - MacPorts (http://www.macports.org/install.php)
 
 
+If you're building manually you need Texinfo version 5.0 or later. The
+simplest way to get it is to use Homebrew (brew install texinfo) and
+then ``export PATH=/usr/local/opt/texinfo/bin:$PATH``.
+
+
 With Gentoo Prefix you can build the release version or the latest
 devel version (-9999) the usual way described in the Gentoo
 documentation. Alternatively, install the prerequisites and build