Many fixes and improvements to the BIOS Extension ROM. (#33)

* Revert "Uploaded_2_9_2025"

This reverts commit ec79bbdbc9.

* Fixing DEBUG_IO builds.

* Make the IO port base a define.

* Fix CPU test to properly handle 808x vs V20.

* Improve timeout management logic.

* Improve SD Card initialization logic.

* Implement INT18h bootstrapping.

* Implementing a different test for processor type.

* Allow use with another fixed drive (eg: ESDI drive).

* Allow swapping driver ID between the BIOS disk and XTMax.

* Fix address of the ROM segment.

* Fixing missing STI at the top of the handler.

* Major rework of IO to use MOVSW.

* More code reorg and auto-detecting second drive.

* Update XTSD to use MOVSW.

* Add diagnostics program.

* Workaround for MS-DOS strange handling of interrupts.

* Use a lookup table for the memory map.

* Make the BootROM relocatable.

* Some more refactor of the Teensy code.

XTMax/Drivers/BootROM/tests.inc

@@ -8,6 +8,7 @@
 
     xor ax, ax
     lahf
+    sti
     mov ax, 0x1122
     mov bx, 0x3344
     mov cx, 0x5566
@@ -114,6 +115,8 @@ do_int13h:
 
     ; dump registers
 %ifdef DUMP_REGS
+    popf
+    pushf
     call dump_regs
     pop ax
     call print_hex
@@ -145,6 +148,11 @@ fake_int13h_entry:
     mov al, ah
     xor ah, ah
     call print_hex
+    mov ax, drive_msg
+    call print_string
+    mov ax, dx
+    xor ah, ah
+    call print_hex
     mov ax, newline
     call print_string
     pop ax
@@ -162,6 +170,7 @@ buf_write           db 1, 2, 3, 4, 5, 6, 7, 8
 buf_read            times 1024 db 0
 
 fake_handler_msg    db 'BIOS INT13h Function ', 0
+drive_msg           db ' Drive ', 0
 test_success_msg    db 'Call succeeded ', 0
 test_failed_msg     db 'Call failed ', 0