INT 13 - QUICKCACHE II v4.20 - SET READ BUFFER SIZE FOR SPECIFIC DRIVE

	AH = 39h
	AL = new size of read buffer
	DL = drive number (00h = A:)
Return: AX = status (0000h successful)
Program: QUICKCACHE II is a shareware disk cache by P.R. Glassel and
	  Associates, Inc.
SeeAlso: AH=2Ah,AH=3Ah