Make all copyright notices include this year.
Most say "2000-2026" but some files created later had later start
dates, and some created last year only had the start date. They now
all have "-2026" regardless.
Closes#340
I have replaced all the "Copyright (C) .* The Xastir Group" lines in
the entire source tree with identical text, "Copyright (C) 2000-2018
The Xastir Group." By making every file have exactly the same text,
this simplifies the operation we have to perform in 2019 when we
update the copyrights.
I also found a few files with DOS-style CRLF line breaks. I have replaced
them with plain LF line breaks.
Also fixed a few "whitespace errors" in db2APRS.c
