Add some notes about Tools/scripts/serve.py.

Tools/scripts/README

@@ -57,6 +57,7 @@ pysource.py		Find Python source files
 redemo.py		Basic regular expression demonstration facility
 reindent.py		Change .py files to use 4-space indents.
 rgrep.py		Reverse grep through a file (useful for big logfiles)
+serve.py		Small wsgiref-based web server, used in make serve in Doc
 setup.py		Install all scripts listed here
 suff.py			Sort a list of files by suffix
 svneol.py		Sets svn:eol-style on all files in directory

Tools/scripts/serve.py

 #!/usr/bin/env python
+'''
+Small wsgiref based web server. Takes a path to serve from and an
+optional port number (defaults to 8000), then tries to serve files.
+Mime types are guessed from the file names, 404 errors are thrown
+if the file is not found. Used for the make serve target in Doc.
+'''
 import sys
 import os
 import mimetypes