t_v_m: dont escape filename when saving attachments
Merge branch 'get-rid-of-extra-slashes' into running
t_v_m: dont escape filename when saving attachments

Extra Shellwords.escaping was introduced in 3106f6d where in reality
only functionality for saving with default filenames should be added.

The Shellwords escaping is removed. The filename is not used in any
command, and any program or command out-of-sup needs to account for
correct filename. The filename may potentially contain shell commands,
the file will be saved with the filename indicated by the SENDER of the
email.

Fixes #277.
move SupSingleton to Redwood::Singleton
Merge #279: Rename SupSingleton to Redwood::Singleton

Replaces #275 and undoes #271 in favor of a Singleton class inside the
Redwood module.
Merge branch 'develop' into maildir-root
async: option for always async
async edit: automatically launch async hook
Merge branch 'always_async_d' into running
async edit: history
completion-mode: correctly set completion character

Auto completion is case-insensitive. Calculation of the completion
character must be case-insensitive as well.

Otherwise, if you have two labels "bar" and "Baz", and you type

    Lba<Tab>

the letters 'b' and 'B' are marked, when really 'r' and 'z' should be
marked. The same goes for contacts with an initial segment that differs
only in case.
ctrl-n, ctrl-p: don't close message if there is no next one

This fixes the following inconsistent behaviour.

- have a thread with multiple messages

old behaviour:

1. close all messages
2. move cursor on a later message
3. repeatedly press ctrl-p until you reach the first message
4. pressing ctrl-p one more time closes the first message again

Step 4. should not close the message. In fact, if you close all but the
first message in step 1, then step 4 doesn't close the message. This is
inconsistent.

new behaviour:

The first message stays open when you press ctrl-p, no matter if it was
opened or closed before.

Analoguous for ctrl-n and the last message in a thread.
Merge branch 'develop' into running
Merge remote-tracking branch 'origin/pr/288' into running
Merge remote-tracking branch 'origin/pr/287' into running
Merge #287: completion-mode: Correctly set completion character
history: bugfixes
Merge branch 'develop' into maildir-root
Merge branch 'maildir-root' into running