[NPANDAY-505] add backup paths for old tools versions

Not all SDKs will set the registry values for these, so look up based on
the following table: http://msdn.microsoft.com/en-us/library/bb397428.aspx

git-svn-id: https://svn.apache.org/repos/asf/incubator/npanday/trunk@1609387 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/components/dotnet-core/src/main/resources/META-INF/npanday/compiler-plugins.xml b/components/dotnet-core/src/main/resources/META-INF/npanday/compiler-plugins.xml
index 06facb0..909ee02 100644
--- a/components/dotnet-core/src/main/resources/META-INF/npanday/compiler-plugins.xml
+++ b/components/dotnet-core/src/main/resources/META-INF/npanday/compiler-plugins.xml
@@ -88,6 +88,7 @@
     </platforms>
     <probingPaths>
       <probingPath>${HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSBuild\ToolsVersions\2.0@MSBuildToolsPath}</probingPath>
+      <probingPath>${env.SYSTEMROOT}\Microsoft.NET\Framework\v2.0.50727</probingPath>
     </probingPaths>
     <commandFilter>
       <includes>
@@ -153,6 +154,7 @@
     </platforms>
     <probingPaths>
       <probingPath>${HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSBuild\ToolsVersions\3.5@MSBuildToolsPath}</probingPath>
+      <probingPath>${env.SYSTEMROOT}\Microsoft.NET\Framework\v3.5</probingPath>
     </probingPaths>
     <commandFilter>
       <includes>
@@ -242,6 +244,7 @@
     </platforms>
     <probingPaths>
       <probingPath>${HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSBuild\ToolsVersions\3.5@MSBuildToolsPath}</probingPath>
+      <probingPath>${env.SYSTEMROOT}\Microsoft.NET\Framework\v3.5</probingPath>
     </probingPaths>
     <commandFilter>
       <includes>