SIGSEGV error on windows
Testing imgui on windows with cimgui.dll built with mingw32-make.exe.

```
import imgui
igText("Hello World")
```
get below error.
```
Traceback (most recent call last)
c:\nim\imgui\main_imgui.nim(3) main_imgui
SIGSEGV: Illegal storage access. (Attempt to read from nil?)
```
I think it is related to cimgui.dll - what is best way to build this.