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INT 21 - DOS 2+ - ADJUST MEMORY BLOCK SIZE (SETBLOCK)
        AH = 4Ah
        ES = segment address of block to change
        BX = new size in paragraphs
Return: CF set on error
            AX = error code (07h,08h,09h) (see AH=59h)
            BX = maximum size possible for the block (if AX=08h)
        CF clear if successful
Notes:  under PCDOS 2.1 and 3.1 and MSDOS 3.2 and 3.3, if there is insufficient
          memory to expand the block as much as requested, the block will be
          made as large as possible
        DOS 3.30 coalesces any free blocks immediately following the block to
          be resized
SeeAlso: AH=48h,AH=49h