Resize Memory Block

Changes the size of a memory block that was previously
allocated with either the Allocate Memory Block function
(Int 31H Fn 0501H) or the Allocate Linear Memory Block
function (Int 31H Fn 0504H).

Call With:

   AX     = 0503H
   BX:CX  = new size of block (bytes, must be nonzero)
   SI:DI  = memory block handle

Returns:

   if function successful
   Carry flag= clear
   BX:CX  = new linear address of memory block
   SI:DI  = new handle for memory block

   if function unsuccessful
   Carry flag= set
   AX     = error code
           8012H   linear memory unavailable
           8013H   physical memory unavailable
           8014H   backing store unavailable
           8016H   handle unavailable
           8021H   invalid value (BX:CX = 0)
           8023H   invalid handle (in SI:DI)

Notes:

o  After this function returns, the previous handle for the
   memory block is invalid and should not be used.
o  When increasing the size of a block, this function always
   creates committed pages.  When decreasing the block size,
   this call will correctly free all possible page types
   (committed pages, uncommitted pages, and mapped pages).
   The linear address and handle of the memory block may
   change  as a result of this call.
o  It is the client's responsibility to update any
   descriptors that map the memory block with the new linear
   address after resizing the block.
o  This function returns an error if the client attempts to
   resize a memory block to zero bytes.