Fix EXITINFO.BBS generation for 64-bit time_t and more

So I was working on re-writing some of this door file generation code and noticed that the EXITINFO.BBS files generated by SBBS:

1. had a lot of garbage data filling unused string characters (no "harm", but potentially leaking information)
2. had the wrong total file length due to 64-bit logontime (time_t)
3. had the wrong total file length due to writing 19 GosubData elements (instead of 20)

The first and last issues appear to be some of those "forever" (20+ year old) bugs.

So I'm guessing no regularly used door games actually use these portions of the EXITINFO.BBS, so most likely: no harm, no foul. But still, best to fix this before I commit the rewrite.