Add dxgi to the proxy export list (#103)

Forward the five dxgi.dll exports (CreateDXGIFactory/1/2,
DXGIDeclareAdapterRemovalSupport, DXGIGetDebugInterface1) so the doorstop
proxy can stand in as dxgi.dll -- the proxy host some titles load instead of
winhttp/version. Same mechanism as the existing version/winhttp lists.

Author: HetCreep

src/windows/proxy/proxylist.txt

@@ -79,4 +79,9 @@ WinHttpWebSocketReceive
 WinHttpWebSocketSend
 WinHttpWebSocketShutdown
 WinHttpWriteData
-WinHttpWriteProxySettings
+WinHttpWriteProxySettings
+CreateDXGIFactory
+CreateDXGIFactory1
+CreateDXGIFactory2
+DXGIDeclareAdapterRemovalSupport
+DXGIGetDebugInterface1