[Reduction] #257: xfflush
[Reduction] #258: C++ delete operator

Lol, "registerbgidriver". Just because the original function is nothing but a
wrapper around free(), and registerbgidriver() is also just a wrapper around
registerfarbgidriver().
[Reduction] #259: C++ delete[] operator

Same for registerbgifont() being a wrapper around registerfarbgifont(). But
at least there, IDA should have noticed something weird. The original delete[]
operator refers to the delete function, so registerbgifont() would have had to
be a wrapper around registerbgidriver(), which of course doesn't make sense,
and IDA claims to *know* these functions...
[Reduction] #260-263: xxas.cpp

Well. Even after downloading pretty much every (identical) copy of Turbo /
Borland C++ 3, 4, 5 and everything inbetween, I could *not* find the original
source to most of the C++ parts in the runtime. Using the IDA disassemblies
to build their slices is simply the only option.

... Really, though, who cares.
[Reduction] #264-267: xalloc.cpp
[Reduction] #268-272: xmsg.cpp

[Binary change] Order of 6 relocations in every executable except for the TH04
ones.
[Reduction] #273: cputype.asm

Don't have the source code for that one either.
[Reduction] #274-323: xx.cpp

Yup. 50 functions in a single module, totalling 12,633 bytes, used in all 15
game executables, and no references to any of that in the remaining game code.

[Binary change]
* Order of 3 relocations in all of THO3, TH04 and TH05, TH02's MAIN.EXE and
  MAINE.EXE, and TH01's OP.EXE and FUUIN.EXE
* Order of 2 relocations in TH02's OP.EXE and TH01's REIIDEN.EXE
* Inserts a new relocation into TH03's MAIN.EXE