gitk: Show notes by default (like git log does)

gitk: Show notes by default (like git log does)

Starting from ~ git-1.6.6, log, show & whatchanged show notes by default.

On the other hand, gitk does not show notes by default, because under
the hood it calls 'git log --pretty=raw ...' to get the log, and in
'git log' notes are turned off when user specifies format or pretty
settings.

Yes, it is possible to invoke 'gitk --show-notes' explicitly, but since
from user's perspective, gitk is gui enabled git log, it would be
logical for gitk to show notes by default too for consistency.

In git, --show-notes was introduced in 66b2ed (Fix "log" family not to
be too agressive about showing notes) which predates 1.6.6.2.

Notes can still be supressed with 'gitk --no-notes'.

Cc: Michael J Gruber <redacted>
Signed-off-by: Kirill Smelkov <redacted>
Signed-off-by: Paul Mackerras <redacted>