Introduce MODESEGMENT define; rename VISIBLE32 to VISIBLE32FLAT.

Prepare for support of segmented 32bit code.
Add new MODESEGMENT definition, and clarify existing 32bit mode defs.
diff --git a/Makefile b/Makefile
index 45f176e..26c9461 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,7 @@
         pnpbios.c pirtable.c vgahooks.c ramdisk.c \
         usb.c usb-uhci.c usb-ohci.c usb-hid.c paravirt.c
 SRC16=$(SRCBOTH) system.c disk.c apm.c pcibios.c font.c
-SRC32=$(SRCBOTH) post.c shadow.c memmap.c coreboot.c boot.c \
+SRC32FLAT=$(SRCBOTH) post.c shadow.c memmap.c coreboot.c boot.c \
       acpi.c smm.c mptable.c smbios.c pciinit.c optionroms.c mtrr.c \
@@ -34,8 +34,8 @@
 COMMONCFLAGS += $(call cc-option,$(CC),-fno-stack-protector,)
 COMMONCFLAGS += $(call cc-option,$(CC),-fno-stack-protector-all,)
-override CFLAGS = $(COMMONCFLAGS) -g -DMODE16=0
-CFLAGS16INC = $(COMMONCFLAGS) -DMODE16=1 -fno-defer-pop \
               $(call cc-option,$(CC),-fno-jump-tables,-DMANUAL_NO_JUMP_TABLE) \
               $(call cc-option,$(CC),-fno-tree-switch-conversion,) \
               $(call cc-option,$(CC),--param large-stack-frame=4,)
@@ -112,36 +112,36 @@
 $(OUT)ccode.16.s: ; $(call whole-compile, $(CFLAGS16) -S, $(addprefix src/, $(SRC16)),$@)
-$(OUT)ccode32.o: ; $(call whole-compile, $(CFLAGS), $(addprefix src/, $(SRC32)),$@)
+$(OUT)ccode32flat.o: ; $(call whole-compile, $(CFLAGS), $(addprefix src/, $(SRC32FLAT)),$@)
 $(OUT)code16.o: romlayout.S $(OUT)ccode.16.s $(OUT)asm-offsets.h
 	@echo "  Compiling (16bit) $@"
 	$(Q)$(CC) $(CFLAGS16INC) -c -D__ASSEMBLY__ $< -o $@
-$(OUT) $(OUT) $(OUT)code32.o: $(OUT)ccode32.o $(OUT)code16.o tools/
+$(OUT) $(OUT) $(OUT)code32flat.o: $(OUT)ccode32flat.o $(OUT)code16.o tools/
 	@echo "  Building ld scripts (version \"$(VERSION)\")"
 	$(Q)echo 'const char VERSION[] = "$(VERSION)";' > $(OUT)version.c
 	$(Q)$(CC) $(CFLAGS) -c $(OUT)version.c -o $(OUT)version.o
-	$(Q)$(LD) -melf_i386 -r $(OUT)ccode32.o $(OUT)version.o -o $(OUT)code32.o
-	$(Q)$(OBJDUMP) -thr $(OUT)code32.o > $(OUT)code32.o.objdump
+	$(Q)$(LD) -melf_i386 -r $(OUT)ccode32flat.o $(OUT)version.o -o $(OUT)code32flat.o
+	$(Q)$(OBJDUMP) -thr $(OUT)code32flat.o > $(OUT)code32flat.o.objdump
 	$(Q)$(OBJDUMP) -thr $(OUT)code16.o > $(OUT)code16.o.objdump
-	$(Q)./tools/ $(OUT)code16.o.objdump $(OUT)code32.o.objdump $(OUT) $(OUT)
+	$(Q)./tools/ $(OUT)code16.o.objdump $(OUT)code32flat.o.objdump $(OUT) $(OUT)
-$(OUT)rom16.o: $(OUT)code16.o $(OUT)rom32.o $(OUT)
+$(OUT)rom16.o: $(OUT)code16.o $(OUT)rom32flat.o $(OUT)
 	@echo "  Linking (no relocs) $@"
 	$(Q)$(LD) -r -T $(OUT) $< -o $@
-$(OUT)rom32.o: $(OUT)code32.o $(OUT)
+$(OUT)rom32flat.o: $(OUT)code32flat.o $(OUT)
 	@echo "  Linking (no relocs) $@"
-	$(Q)$(LD) -r -T $(OUT) $< -o $@
+	$(Q)$(LD) -r -T $(OUT) $< -o $@
-$(OUT)rom.o: $(OUT)rom16.o $(OUT)rom32.o $(OUT) $(OUT)
+$(OUT)rom.o: $(OUT)rom16.o $(OUT)rom32flat.o $(OUT) $(OUT)
 	@echo "  Linking $@"
-	$(Q)$(LD) -T $(OUT) $(OUT)rom16.o -R $(OUT)rom32.o -o $(OUT)rom16.reloc.o
+	$(Q)$(LD) -T $(OUT) $(OUT)rom16.o -R $(OUT)rom32flat.o -o $(OUT)rom16.reloc.o
 	$(Q)$(STRIP) $(OUT)rom16.reloc.o -o $(OUT)
 	$(Q)$(OBJCOPY) --adjust-vma 0xf0000 $(OUT)rom16.o $(OUT)rom16.moved.o
-	$(Q)$(LD) -T $(OUT) $(OUT) $(OUT)rom32.o -R $(OUT)rom16.moved.o -o $@
+	$(Q)$(LD) -T $(OUT) $(OUT) $(OUT)rom32flat.o -R $(OUT)rom16.moved.o -o $@
 $(OUT)bios.bin.elf $(OUT)bios.bin: $(OUT)rom.o tools/
 	@echo "  Prepping $@"