Minor updates to the OS X installer ReadMe.rtf.

Mac/BuildScript/resources/ReadMe.rtf

-{\rtf1\ansi\ansicpg1252\cocoartf1343\cocoasubrtf160
+{\rtf1\ansi\ansicpg1252\cocoartf1347\cocoasubrtf570
 {\fonttbl\f0\fswiss\fcharset0 Helvetica;\f1\fmodern\fcharset0 CourierNewPSMT;}
 {\colortbl;\red255\green255\blue255;}
 \margl1440\margr1440\vieww13380\viewh14600\viewkind0
@@ -23,8 +23,8 @@ Python.org provides two installer variants for download: one that installs a
 \i $MACOSX_DEPLOYMENT_TARGET
 \i0  variant.  Unless you are installing to an 10.5 system or you need to build applications that can run on 10.5 systems, use the 10.6 variant if possible.  There are some additional operating system functions that are supported starting with 10.6 and you may see better performance using 64-bit mode.  By default, Python will automatically run in 64-bit mode if your system supports it.  Also see 
 \i Certificate verification and OpenSSL
-\i0  below.
-\b \ul \
+\i0  below.  The Pythons installed by these installers are built with private copies of some third-party libraries not included with or newer than those in OS X itself.  The list of these libraries varies by installer variant and is included at the end of the License.rtf file.
+\b \ul \ulc0 \
 \
 Update your version of Tcl/Tk to use IDLE or other Tk applications
 \b0 \ulnone \