git-gui: Delay the GC hint until after we are running

git-gui: Delay the GC hint until after we are running

I'm moving the code related to looking to see if we should GC now
into a procedure closer to where it belongs, the database module.
This reduces our script by a few lines for the single commit case
(aka citool).  But really it just is to help organize the code.

We now perform the check after we have been running for at least
1 second.  This way the main window has time to open up and our
dialog (if we open it) will attach to the main window, instead of
floating out in no-mans-land like it did before on Mac OS X.

I had to use a wait of a full second here as a wait of 1 millisecond
made our console install itself into the main window.  Apparently we
had a race condition with the console code where both the console and
the main window thought they were the main window.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>