INT 2A,81 - End DOS Critical Section

	AH = 81h
	AL = critical section identifier (00-0F)
	   = 01  DOS kernel, SHARE.EXE and network data structure integrity
	   = 02  DOS kernel, device driver exclusivity
	   = 05  IFSFUNC (Installable File System, IFS, DOS 4.0+)
	   = 06  IFSFUNC (Installable File System, IFS, DOS 4.0+)
	   = 08  ASSIGN.COM


	returns nothing


	- indicates that a critical code section is being exited
	- this function is usually hooked rather then called directly from a
	  user application
	- see  Bibliography reference to "Undocumented DOS"