Fix and cleanup saving

Hi Serge,
this pull request addresses two issues of the rewritten save functionality which I contributed last time.

The probably most important change (1676247) fixes the segment alignment. The copied elf files can now be properly executed.

The second interesting change (91e61ec) enables the use of the regular API to build up ELF files with segments which start at offset 0 by adding the NULL section to the segment. The previous version used the offset information which can not be written via the API and therefore only worked with loaded ELF files.

The other commits are more of cosmetic nature.

Regards,
niosHD