SaveFileDialog changes working directory, but only on Windows
EDIT2: By now I managed to figure out what was causing my problems. Code isn't neccessary. The Problem was that using a SaveFileDialog will change the working directory of the program to the folder in which the selected File is stored. BUT to add insult to injury, this is only the case for Windows, not for Linux. I dont think that's a real bug, but I think the behavior should be the same on both platforms.  

Feel free to close this again if you disagree.

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EDIT: Nvm, I was trying to reproduce the bug with a minimal example for hours, and in my delusion I forgot to add the required text file ... Ill reopen this once I manage to actually reproduce the problem ...

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The following example will either crash, or freeze if compiled with `--gc:arc`

```nim
import nigui

app.init()

var 
    win = newWindow("Session Planer")
    drawing = newControl()

drawing.widthMode = WidthMode_Expand
drawing.heightMode = HeightMode_Expand
win.add(drawing)

drawing.onDraw = proc(ev: DrawEvent) = 
    discard readFile "foo.txt"
    quit(0)

win.show()
app.run()
```

The line where it freezes is the one with `readFile`.
This happens only on Windows 10 but not on Ubuntu. It happens with mingw and msvc. Tested with nigui 0.2.4 and 0.2.5 (the --gc:arc option was only tested with 0.2.4)

Btw, this might be related to #112 
