Added batch file for running 'BuildSilverlight2'

build/Build.bat

@@ -1,5 +1,5 @@
 @echo off
 
-%WINDIR%\Microsoft.NET\Framework\v4.0.30319\msbuild build.csproj /m /p:BuildConfiguration=Debug
+%WINDIR%\Microsoft.NET\Framework\v4.0.30319\msbuild build.csproj /m /t:Build /p:BuildConfiguration=Debug
 
 pause

build/BuildSilverlight2.bat

@@ -0,0 +1,5 @@
+@echo off
+
+%WINDIR%\Microsoft.NET\Framework\v4.0.30319\msbuild build.csproj /m /t:Build /p:BuildConfiguration=Debug_Silverlight2
+
+pause

build/build.csproj

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
 	<PropertyGroup>
 		<ProjectName>Protocol Buffers</ProjectName>