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 call may be made from within a hardware interrupt handler
SeeAlso: AX=101Ch,AX=DE13h,AX=DE1Bh

See also: 15101B

15DE1C - DESQview v2.23+ - "ENTERC" - INCREMENT CRITICAL NESTING COUNT