download_cmd behind behind a corporate proxy

[GeraldKaeferle]

Hi,
I use julia in a MS Windows enviroment behind a corporate proxy. On some tests with Blink i mentioned a problem with download_cmd in BinDeps. Our proxy replied an error 407 for proxy authentication.

After changing in function download_cmd the elseif branch for elseif endswith(string(downloadcmd), "powershell") with this code
return `$downloadcmd -NoProfile -Command "\$wc=(new-object net.webclient);\$wc.UseDefaultCredentials = \$true; \$wc.Proxy.Credentials = \$wc.Credentials; \$wc.DownloadFile(\"$url\", \"$filename\")"`
it worked for me.

Please check if this adaption is suitable for other users, aswell.
Source Stackoverflow : PowerShell, Web Requests, and Proxies

Gerald