Inline functions cause cyclic dependencies

[FiniteReality]

Describe the issue:
Some inline functions in our header files cause cyclic dependencies - particularly ones with pointer casts.

Please provide the steps to reproduce if possible:

1. Use the new project structure
2. Try to build a file which includes a header with an inline function
3. Cry

Expected behaviour:
NovelRT should build successfully.

Please tell us about your environment:
This isn't environment-specific.

Additional context:
Eventually we're going to have to discuss what the best approach here is.