Clean up Windows style

[stuartmorgan]

The Windows code hasn't been consistent about following Google's style recommendations on Windows code. Notably:

• We shouldn't ever be using Hungarian notation for variable names.
• Pointer types shouldn't use the composite Windows types (e.g., LP...).

[stuartmorgan]

(This should be done in the engine as well, but just filing once since I'll probably do all of it at once.)