Both files can now be included independently without causing problems.
This also required moving some inline functions into separate files and splitting off the GC definitions from dobject.h to ensure that r_defs does not need to pull in any part of the object hierarchy.
Most of those which still rely on ZDoom's own definition should be gone, unfortunately the code in files that include Windows headers is a gigantic mess with DWORDs being longs there intead of ints, so this needs to be done with care. DWORD should only remain where the Windows type is actually wanted.
Converting a floating point value that is out of range for a signed integer will result in 0x80000000 with SSE math, which is used exclusively for this purpose on modern Visual C++ compilers, so this cannot be used anywhere.
On ARM there's problems with float to unsigned int conversions.
xs_Float does not depend on these
