Further header & precompiled cleanup, fix no-PCH builds.
GUIObjectBase is made a IGUIObject* to avoid including those headers un-necessarily. Subsequent diffs ought to clean up the various of pointers for that with a similar type with reference semantics.
Also:
- Add standard C and C++ headers (mostly cstring for memcpy, string and vector) where needed.
- Swap out some includes for forward declarations
- Clean up un-necessary boost includes in precompiled and other headers.
- Clean up precompiled headers, including fewer things.
- Move ACPI to the windows-specific folder as it's included there only and mostly specific to that platform.
Thanks Stan for the testing.
Differential Revision: https://code.wildfiregames.com/D3129