PSA: contribution checklist: format of git log entries

[Doug Evans via gdb-patches]

Hi.

I was going to send this earlier but just never got around to it.
I think it was last year, or maybe even longer ago, someone (Gary?)
suggested adding paths to the ChangeLog files in the commit message.
It's fine by me, and it's in the contribution checklist:

https://sourceware.org/gdb/wiki/ContributionChecklist#Properly_Formatted_GNU_ChangeLog

I think things may have changed a bit as the format that's there now
is slightly different than I remember it. Anyways, it's in the
contribution checklist which I think we're all supposed to follow.

So heads up.

Instead of this:

    2017-02-03  Im Dave  <im@dave.com>

            * foo.c (bar): Fix baz.

    2017-02-03  Im Dave  <im@dave.com>

            * gdb.base/foo.exp: Add new tests.

This:

    gdb/ChangeLog:
    2017-02-03  Im Dave  <im@dave.com>

            * foo.c (bar): Fix baz.

    gdb/testsuite/ChangeLog:
    2017-02-03  Im Dave  <im@dave.com>

            * gdb.base/foo.exp: Add new tests.

Though lots of people do this in the commit message, which is fine too UUIC.

    gdb/ChangeLog:

            * foo.c (bar): Fix baz.

    gdb/testsuite/ChangeLog:

            * gdb.base/foo.exp: Add new tests.