build: drop xulrunner configuration options

(integrated from master branch change 5209eae by Todd Whiteman <toddw@activestate.com>)
build: mozilla: drop mozApp variations - just support komodo

(integrated from master branch change d1ad93b by Todd Whiteman <toddw@activestate.com>)
build: mozilla: drop comments about mozApp

(integrated from master branch change 96d1eb6 by Todd Whiteman <toddw@activestate.com>)