Add MSU extractor

If you do patch test/analysis/diffing, you might find this tool
handy. This tool will automatically extract all the *.msu files,
and then you can search for the patched files you're looking for
quickly.

The workflow would be something like this:

1. You download the patches from:
   http://mybulletins.technet.microsoft.com/BulletinPages/Dashboard

2. You put all the *.msu files in one directory.

3. Run this tool: extract_msu.bat [path to *.msu files]

4. The tool should extract the updates. After it's done, you can
   use Windows to search for the file(s) you're looking for.

tools/extract_msu.bat

@@ -0,0 +1,30 @@
+@echo off
+@setlocal EnableDelayedExpansion
+
+@set arg=%~1
+
+if [%arg%] == [] (
+	echo Argument Missing:
+	echo You must provide a directory that contains
+	echo all the Windows patches in *.msu format.
+	echo To Download patches manually, please go:
+	echo http://mybulletins.technet.microsoft.com/BulletinPages/Dashboard
+	exit /B
+)
+
+
+for /f %%f in ('dir /B %arg%') DO (
+	@set fname=%%f
+	@set lastfourchars=!fname:~-4,4!
+	if "!lastfourchars!" == ".msu" (
+		@set newname=!fname:~0,-4!
+		7za e !fname! -o!newname!
+		mkdir !newname!\extracted
+		expand /F:* !newname!\!newname!.cab !newname!\extracted
+	)
+)
+
+echo Done!
+echo Now go to %arg%,
+echo and then use the search feature from Windows to
+echo find the files you're interested in.