[obv] Merge gdb/common/Changelog to gdb/ChangeLog [Re: [rfa/rfc] Build libcommon.a for gdb and gdbserver]

[Tom Tromey]

Yao> common/ dir is to contain the common files for gdb and gdbserver, so it
Yao> should have its own changelog file.  IMO, we may have to revert this
Yao> patch, what do you think?

I would prefer us to have fewer ChangeLogs, not more.

Fixing up the ChangeLogs before submission and then again before commit
is a real chore.  It is somewhat less of a chore when there are fewer
entries.  Also, many patches span directories, and I think it is easier
to see that when the entries are all in a single ChangeLog.  Conversely,
I don't think there is any benefit to having different ChangeLogs in a
single "maintenance domain".

Tom