Focusing on the diskimg library this time, which deals with a lot of
filesystem structures that have specific widths.
This is still a bit lax in places, e.g. using "long" for lengths.
Should either specify a bit width or use di_off_t.
Also, added "override" keyword where appropriate.
Also, bumped library version to 5.0.0.
This updates all source files to use spaces instead of tabs for
indentation. It also normalizes the end-of-line markers to be
Windows-style CRLF, and ensures that all files end with EOL.
No substantive changes were made; "diff -w" is empty.