Error when using `import`.

[Liam McGillivray]

I have made some progress on this. For the raylib front-end, I 
tried making a class called `Mission` which inherits `Map`. This 
class handles the graphics, input, and other game events. The 
program now compiles without errors, and there are some graphics. 
I have pushed these updates to the GitHub repository.
https://github.com/LiamM32/Open_Emblem

Currently, it just displays a map of grass tiles with one unit. 
Clicking on the unit causes a segmentation fault. There is 
something that's supposed to happen when clicked, but I don't 
know why it segfaults. The line where it segfaults appears to be 
roughly `oe-raylib/source/mission.d:125`.

I am continuing to work on this, but have been getting more 
strange runtime errors since the latest push.