INT 15 - DESQview v2.23+ - "ENTERC" - INCREMENT CRITICAL NESTING COUNT
	AX = DE1Ch
Return: nothing
Notes:	similar to AX=101Bh, but begins the critical region without ensuring
	  that DOS is free
	the official documentation states that this call should be paired with
	  "ENDC" (AX=101Ch); no mention is made of AX=DE1Bh
	this API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. call may be made from within a hardware interrupt handler
SeeAlso: AX=101Bh,AX=101Ch,AX=DE13h,AX=DE1Bh