win32: Fix crash with -v if stream redirection setup fails

Properly check for errors when setting up debug console stream
redirections so if it fails it doesn't crash everything.
Make the tools->terminal setting more flexible.

Previously was hard coded with options to suit xterm.  As this is
being replaced with different terminal programs some do not accept
the same options.  The new setting stores the whole command with
%c to substitute the script name.  Upgrades old settings if a new
one does not exist.
Fix GTK default keybindings being still active after being unbound

If we provide an AccelGroup when creating a menu item using a sock ID,
it installs the GTK default accelerator, accelerator we can't remove
since we don't know about it.  So, don't give an AccelGroup so GTK
don't install it's own accelerator.

This fix also required to properly update the accelerator on some item
we used to ignore since the update didn't work anyway (since the GTK
accelerator was displayed instead).

Note that this doesn't fix the fact the editor popup menu accelerators
are never updated after startup so they don't get updated before
restart after changing a keybinding in the preferences.  This is a
separate (and less problematic) issue due to a simple lack of update.

Closes #1912683 and #3599251.
Allow Quit keybinding to be configured

This removes the last unmodifiable keybinding relying on GTK's
defaults, and allows somebody to change this keybinding.
Adjust Terminal tooltip in preferences

Adjust to say it is a full command and that %c is substituted by
the geany_run_script path.
Merge branch 'master' of https://github.com/geany/geany
Add missing slash in default command
Merge remote-tracking branch 'upstream/master' into iss3579842