[Maintenance] Move the bgimage_*() functions to the hardware/ directory

Not that it really fits there either, but I've been trying to keep the
th0?/ directories free from any actual code. They should only contain
the distinct translation units within the original three .EXE binaries,
`#include`ing files from subdirectories, along with maybe game-specific
`#pragma`s, but contain no code on their own. Port authors would simply
ignore those, and link everything from the subdirectories into one
binary. That approach has seemed to make the most sense for all of this
so far.

Part of P0135, funded by [Anonymous].

th04_maine.asm

@@ -4615,8 +4615,8 @@ include th02/initmain.asm
 		db    0
 include th04/hardware/input_s.asm
 include th04/snd/se.asm
-include th04/bgimage.asm
-include th04/bgimage_put_rect.asm
+include th04/hardware/bgimage.asm
+include th04/hardware/bgimage_put_rect.asm
 	extern CDG_LOAD_SINGLE_NOALPHA:proc
 	extern CDG_LOAD_SINGLE:proc
 	extern CDG_FREE:proc
@@ -4667,7 +4667,7 @@ include th04/snd/snd[data].asm
 include th04/snd/load[data].asm
 include th04/hardware/grppsafx[data].asm
 include th03/snd/se_state[data].asm
-include th04/bgimage[data].asm
+include th04/hardware/bgimage[data].asm
 include th03/formats/cdg[data].asm
 include th03/formats/pi_put_masked[data].asm
 include th04/end/box[data].asm

th04_op.asm

@@ -2667,8 +2667,8 @@ include th04/formats/cdg_put_noalpha.asm
 include th04/hardware/input_s.asm
 include th04/snd/se.asm
 include th04/hardware/egcrect.asm
-include th04/bgimage.asm
-include th04/bgimage_put_rect.asm
+include th04/hardware/bgimage.asm
+include th04/hardware/bgimage_put_rect.asm
 SHARED	ends
 
 SHARED_	segment	word public 'CODE' use16
@@ -2787,7 +2787,7 @@ include th04/snd/snd[data].asm
 include th04/snd/load[data].asm
 include th04/hardware/grppsafx[data].asm
 include th03/snd/se_state[data].asm
-include th04/bgimage[data].asm
+include th04/hardware/bgimage[data].asm
 include th03/formats/cdg[data].asm
 include th04/setup[data].asm
 include th04/zunsoft[data].asm

th05/m_char.cpp

@@ -14,7 +14,7 @@ extern "C" {
 #include "th01/ranks.h"
 #include "th02/hardware/frmdelay.h"
 #include "th04/formats/cdg.h"
-#include "th04/bgimage.h"
+#include "th04/hardware/bgimage.h"
 #include "th04/score.h"
 #include "th04/common.h"
 #include "th05/chars.h"

th05_maine.asm

@@ -7531,11 +7531,11 @@ include th04/snd/detmodes.asm
 include th04/hardware/grppsafx.asm
 include th04/formats/cdg_put_noalpha.asm
 include th04/snd/se.asm
-include th04/bgimage.asm
+include th04/hardware/bgimage.asm
 include th02/exit.asm
 include th04/math/vector1_at.asm
 include th04/math/vector2_at.asm
-include th04/bgimage_put_rect.asm
+include th04/hardware/bgimage_put_rect.asm
 	extern SND_LOAD:proc
 	extern SND_KAJA_INTERRUPT:proc
 	extern PI_PUT_QUARTER_MASKED_8:proc
@@ -7593,7 +7593,7 @@ include libs/master.lib/bgm[data].asm
 include th04/snd/se_priority[data].asm
 include th04/hardware/grppsafx[data].asm
 include th03/snd/se_state[data].asm
-include th04/bgimage[data].asm
+include th04/hardware/bgimage[data].asm
 include th05/mem[data].asm
 include th05/snd/load[data].asm
 include th04/snd/snd[data].asm

th05_op.asm

@@ -2532,7 +2532,7 @@ include th02/exit_dos.asm
 include th04/hardware/grppsafx.asm
 include th04/formats/cdg_put_noalpha.asm
 include th04/snd/se.asm
-include th04/bgimage.asm
+include th04/hardware/bgimage.asm
 include th04/formats/cdg_put.asm
 include th02/exit.asm
 include th04/math/vector1_at.asm
@@ -2540,7 +2540,7 @@ include th04/math/vector2_at.asm
 include th05/music/piano.asm
 GRCG_SETCOLOR_DIRECT_DEF 1
 		db 0
-include th04/bgimage_put_rect.asm
+include th04/hardware/bgimage_put_rect.asm
 	extern SND_LOAD:proc
 	extern SND_KAJA_INTERRUPT:proc
 	extern PI_PUT_MASKED_8:proc
@@ -2660,7 +2660,7 @@ include libs/master.lib/bgm[data].asm
 include th04/snd/se_priority[data].asm
 include th04/hardware/grppsafx[data].asm
 include th03/snd/se_state[data].asm
-include th04/bgimage[data].asm
+include th04/hardware/bgimage[data].asm
 include th05/mem[data].asm
 include th05/music/piano[data].asm
 include th05/sprites/piano_l.asp