Set Debug Watchpoint

Sets a debug watchpoint at the specified linear address.

Call With:

   AX     = 0B00H
   BX:CX  = linear address of watchpoint
   DL     = size of watchpoint (1, 2, or 4 bytes)
   DH     = type of watchpoint
           0 = execute
           1 = write
           2 = read/write

Returns:

   if function successful
   Carry flag= clear
   BX     = watchpoint handle

   if function unsuccessful
   Carry flag= set
   AX     = error code
           8016H   too many breakpoints
           8021H   invalid value (in DL or DH)
           8025H   invalid linear address (linear address
                   not mapped or alignment error)

Notes:

o  Under DPMI 1.0, the handle will be in the range 0-14.
   Under DPMI 0.9, the handle range is not limited.
o  The watchpoint handle corresponds to the bit number in
   the Virtual DR6 returned in the exception frame (see Int
   31H Fn 0212H and page 18).