INT 21,5D - Critical Error Information (Undocumented, DOS 3.x+)

	See second reference below for more information about this interrupt
	information presented here is incomplete

	AH = 5D
	AL = 00  server function call  (DOS 3.1+)
	   = 01  commit all files  (DOS 3.1+)
	   = 02  SHARE: close file by name  (DOS 3.1+)
	   = 03  SHARE: close all files for given computer  (DOS 3.1+)
	   = 04  SHARE: close all files for given process  (DOS 3.1+)
	   = 05  SHARE: get open file list entry  (DOS 3.1+)
	   = 06  get address of DOS swappable area into DS:SI  (DOS 3.0+)
	   = 07  get network redirected printer mode  (DOS 3.1+)
	   = 08  set network redirected printer mode  (DOS 3.1+)
	   = 09  flush network redirected printer output  (DOS 3.1+)
	   = 0A  set extended error information  (DOS 3.1+)
	   = 0B  get DOS swappable data areas  (DOS 4.x+)
	DS:DX = pointer to 18 byte DOS Parameter List (DPL, if AL=00)
	      = pointer to 9 byte data block of the form (AL=0A):

	      Offset Size	Description

		00   word   extended error code to set
		02   dword  pointer to driver address to set
		06   byte   action code to set
		07   byte   class code to set
		08   byte   locus code to set

	on return:
	DS:SI = (if AL was 6) address of critical flag of the form:

	      Offset Size      Description

		00   word   extended error code
		02   byte   action code
		03   byte   class code
		04   byte   pointer to driver address

	- function 0 copies 18 bytes from DS:SI to the DOS internal
	  register-save area;  this data will be placed in the registers
	  when DOS returns to the caller thereby circumventing the DOS
	  register save logic
	- may be used by a TSR to prevent accidental changing of an error
	  code and causing problems in the foreground process
	- see bibliography references for "Undocumented DOS" and "DOS
	  Programmers Reference"

	- see	INT 21,59