when run in repos other than gcc mklog fails to find ChangeLog files
because it looks for $0/../$dir/ChangeLog, but of course if the diff is
for a project other than gcc that might not exist.  It should be fine to
also look for $cwd/$dir/ChangeLog, and use that if we find it.  This
means that for example in binutils-gdb.git you can do git commit,
and then in your editor read git diff HEAD~ | mklog - to generate a
template ChangeLog for that commit.

contrib/ChangeLog:

2016-03-06  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* mklog: Look for the ChangeLog file in $cwd.

From-SVN: r234014