navig_driver.js: fix highlighting using a stack of events, with push and pop operations
based on events enter and exit in the run_expr function.
That is, deal better with src_next and src_prev by looking at
the context that has an term in it with an enter or an exit event
From #26 :
navig_driver.js: fix highlighting using a stack of events, with push and pop operations based on events enter and exit in the run_expr function. That is, deal better with src_next and src_prev by looking at the context that has an term in it with an enter or an exit event