Pass $now to tab_activity_mark to avoid calling urxvt::NOW all the time

µoptimisation.  Probably does not make any difference, but somehow
makes sense to me. ;)
Allow overwriting of the initial activity mark character

-1 was not accepted as a valid timeout anad besides it makes more
sense for 0 being the timeout for the initial activity mark.  Changing
comparison from > to >= moves all marks by one second (which somehow
alters the behaviour of the resource but it should not be too visible
to users) and lets 0 match initial output.
Add support for matching activity characters

“(0(” does not look nice at all… “(0)” looks much better. :)
Introduce bell handling by displaying tabs in a different color
Rename lastActivity to last_activity to be consistant in naming
Introduce rs_bool function and rename my_resource to rs_text

Addition of rs_bool removes some duplicated code (namely regex
matching) and makes things cleaner.  The rs_* prefix is now
intended to be used for functions that read and intepret resources.
Allow auto hiding the tab bar even if tab is named

Previous versions did not autohide the tab bar if the remaining
tab had a name (as opposed to an index number).  I think "autohide"
means "autohide", so I changed that behaviour.

[mina86@mina86.com: added a fix to temporarily show the tab bar
 while renaming a tab]
Added tabbedx;set_tab_name OSC handler

This lets one change the name of the current tab from within the
tab by running:

    printf "\033]777;tabbedx;set_tab_name;new name\007"

or something equivalent.

[mina86@mina86.com: tiny refactoring]
Show current tab visible on tab bar even if there are a lot of open tabs

Previously, if you had a lot of tabs and/or tabs with long names,
the current tab might not show up in the tab bar (if its position
in the tab name string was more than $self->ncol chars from the
beginning).  Changes below ensure that the name of the current tab
is always visible.  Arguably it would be nice to have indications
at each end showing whether there are more tabs in that direction.

Also, when printing the tab bar, limit the length of the tab
names so that one tab name doesn't occupy the whole tab bar.

[mina86@mina86.com: tiny refactoring]
Add missing hook for on_tt_write in tabbed extension

With this change pty input written with tt_write is properly dispatched
to the active tabbed window when events are sent to the main window.
Patch by Martin Pohlack.

[mina86@mina86.com: pulled from r1.26 in rxvt-unicode CSV repository]
Remove unused variable

[mina86@mina86.com: pulled form r1.28 in rxvt-unicode CSV repository]