RBIL61 - INT 2F - DOS 3.0+ CRITICAL ERROR HANDLER - EXPAND ERROR INTO STRING {callout or callback, undocumented}

INT 2F CU - DOS 3.0+ CRITICAL ERROR HANDLER - EXPAND ERROR INTO STRING          
	AH = 05h
---DOS 3.x---
	AL = extended error code (not zero)
---DOS 4.0+ ---
	AL = error type
	    01h DOS extended error code
	    02h parameter error
	BX = error code
Return: CF clear if successful
	    ES:DI -> ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. error message (read-only)
	    AL = completion state
		00h message requires completion with device name, drive, etc.
		01h message is complete as returned
	CF set if error code can't be converted to string
	    AX,DI,ES destroyed
	other flags corrupted
Notes:	called at start of COMMAND.COM's default critical error handler if
	  installed by a user program, allowing partial or complete overriding
	  of the default error messages
	subfunction 02h is called by many DOS 4 external programs
	DR DOS's COMMAND.COM appends additional info ("0 files copied") to the
	  returned string
SeeAlso: AX=0500h,AX=122Eh,INT 24