Change update size for PBA (#419)

Change update size for PBA (#419)

When using PBA, file size was used to calculate next base address of assembly.
However, there is a problem that the file size is smaller than the image size loaded in the actual memory.
when native image files are loaded in the memory area, some native image files cannot be loaded where desired because of area overlapping.

So, get size of image from OptionalHeader, and use that value for updating next base address.