v1.27

   - added new variant DEBUGXU.COM. This version does not use int 15h, 
     ah=87h inside the DX command, thus avoiding to disable a possibly
     active unreal mode. The catch is that this version's DX command won't
     work in V86 mode.
   - disassembler handles operand size prefix for one-byte "push <imm>" 
     opcodes correctly. OTOH, for 2/4 byte "push <imm>" opcodes, the 
     disassembler no longer displays the operand size, since the size
     is obvious.
   - if InDOS flag is set, a '!' is preceding the debugger prompt.
   - BIOS used when waiting for a key in help msg display.
   - 'e' cmd uses BIOS if InDOS flag set.