bpo-32726: macOS installer and framework enhancements and changes for 3.7.0 (GH-5448)

This issue covers various changes for the macOS installers provided via python.org for 3.7.0.

- Provide a provisional new installer variant for macOS 10.9 and later systems with 64-bit (x86_64) architecture only.  Apple has made it known that future versions of macOS will only fully support 64-bit executables and some other third-party software suppliers have chosen 10.9 as their oldest supported system.
 
- Support **Tcl/Tk 8.6** with the 10.9 installer variant.
 
- Upgrade **OpenSSL** to 1.1.0g and **SQLite** to 3.22.0.
 
- The compiler name used for the interpreter build and for modules built with **Distutils / pip** is now _gcc_ rather than _gcc-4.2_. And extension module builds will no longer try to force use of an old SDK if present.
diff --git a/Mac/BuildScript/resources/Welcome.rtf b/Mac/BuildScript/resources/Welcome.rtf
index 528e251..18f3290 100644
--- a/Mac/BuildScript/resources/Welcome.rtf
+++ b/Mac/BuildScript/resources/Welcome.rtf
@@ -1,4 +1,4 @@
-{\rtf1\ansi\ansicpg1252\cocoartf1504\cocoasubrtf830
+{\rtf1\ansi\ansicpg1252\cocoartf1561\cocoasubrtf200
 \cocoascreenfonts1{\fonttbl\f0\fswiss\fcharset0 Helvetica;}
 {\colortbl;\red255\green255\blue255;}
 {\*\expandedcolortbl;;}
@@ -19,7 +19,11 @@
 \
 
 \b NOTE:
-\b0   This is an early developer preview of the next feature release of Python 3.  Many features are yet to be added and existing features may change substantially or be deleted prior to the feature code freeze.\
+\b0   This is an beta preview of the next feature release of Python 3.  New features may change substantially or be deleted prior to the final code freeze.\
+\
+
+\b NEW in 3.7.0b1: 
+\b0 two installer variants (10.9+ 64-bit-only, 10.6+ 64-/32-bit), Tcl/Tk 8.6 support in the 10.9+ variant, OpenSSL 1.1.0g, and more!\
 \
 
 \b IMPORTANT: