I spotted a few misplaced entries in the ChangeLog-2019 entries, and
went on to fix them.
Looking around I saw a good number of other entries in other years.
Then OCD got the best of me and I fixed them all.
Also fixes cases of wrong paths in entries, like "* gdb/foo.c" instead
of "* foo.c".
This patch renames gdb/'s ChangeLog to ChangeLog-2014 and creates
a new one for 2015. config/djgpp/fnchange.lst is updated accordingly.
gdb/ChangeLog:
* config/djgpp/fnchange.lst: Add entry for gdb/ChangeLog-2014.