fix for bug #342890, make tab min width 125 px by default (down from 140 px)
and heed the hidden browser.tabs.tabMinWidth pref.
fix for bug #342385, get the hidden browser.tabs.tabClipWidth pref working.
It was actually working, but I've changed the default to 115 px to match
the 125 px default value for the browser.tabs.tabMinWidth pref.
also, some code cleanup and whitespace fixes.
r=mano, ui-r=beltzner
git-svn-id: svn://10.0.0.236/trunk@232741 18797224-902f-48f8-a5cc-f745e15eee43