Updates .vcxproj files to Visual Studio 2013 while still building against VS2012 platform

UpdateVcxprojFiles.ps1

function UpdateVcxprojFile($filename) {
    $content = [xml](Get-Content -Path $filename)
    $changed = $false

    $toolsVersion = $content.Project.ToolsVersion
    if ($toolsVersion -ne "12.0") {
        $content.Project.ToolsVersion = "12.0"
        $changed = $true
    }
  
    foreach ($propGroup in $content.Project.PropertyGroup) {
        if ($propGroup.Label -ne "Configuration") {
            # Only PropertyGroups with Label "Configuration" specify a build configuration
            continue
        }

        # set PlatformToolset; "v110" means Visual Studio 2012
        if ($propGroup.PlatformToolset -eq $null) {
            # no PlatformToolset specified yet
            $elem = $content.CreateElement('PlatformToolset', $content.DocumentElement.NamespaceURI)
            $elem.InnerText = "v110"
            $propGroup.AppendChild($elem) | out-null
            $changed = $true
        } elseif ($propGroup.PlatformToolset -ne "v110") {
            # change PlatformToolset
            $propGroup.PlatformToolset = "v110"
            $changed = $true
        }
    }

    if ($changed) {
        Write-Output "Updating $filename"

        &"tf" checkout /lock:none "$filename" /noprompt 2>&1 | Out-Null
        $content.Save($filename)
    }
}

gci *.vcxproj -Recurse | foreach {
    UpdateVcxprojFile($_.Fullname)
}