1) when we have "too many" tabs in a window, allow the user to scroll through
the tabs.
2) add events for when adding and removing tabs
initial patch by mconnor. final patch r=mconnor
and includes the supplimental fixes for:
fix for bug #342364: set the clicktoscroll attribute on the pinstripe
specific binding for tabbrowser. Otherwise, the tabs will scroll on mouseover.
fix for bug #343054: js errors when changing certain browser.tabs.* prefs
r=mconnor,ben a=mconnor,schrep
git-svn-id: svn://10.0.0.236/branches/MOZILLA_1_8_BRANCH@201207 18797224-902f-48f8-a5cc-f745e15eee43
