INT 21 - DOS 2+ - RESIZE MEMORY BLOCK
        AH = 4Ah
        BX = new size in paragraphs
        ES = segment of block to resize
Return: CF clear if successful
        CF set on error
            AX = error code (07h,08h,09h) (see AH=59h)
            BX = maximum paragraphs available for specified memory block
Notes:  under DOS 2.1-5.0, if there is insufficient memory to expand the block
          as much as requested, the block will be made as large as possible
        DOS 2.1-5.0 coalesces any free blocks immediately following the block
          to be resized
SeeAlso: AH=49h,AH=83h