Upgraded embedded Python to 3.7.9 for Windows builds

[skip travis]

appveyor.yml

@@ -85,7 +85,7 @@ install:
 # Get Python embeddable and install packages
 - ps: >-
     if (-not (Test-Path 'C:\Python')) {
-      Start-FileDownload "https://www.python.org/ftp/python/3.7.7/python-3.7.7-embed-amd64.zip" Python.zip
+      Start-FileDownload "https://www.python.org/ftp/python/3.7.9/python-3.7.9-embed-amd64.zip" Python.zip
       7z x Python.zip -oC:\Python\
       echo python37.zip . '' 'import site' | Out-File C:\Python\python37._pth -Encoding ascii
       mkdir C:\Python\lib\site-packages

src/Python/requirements.txt

@@ -1,3 +1,4 @@
+#### Packages for embedded Python ###
 #
 # Core Tools
 #