replace assert by throw new AssertionError

[Jonathan Gibbons]

Team,

javac currently contains assertion statements, and goes out of its way 
to ensure assertions are enabled.
As such, it would seem better to replace "assert cond: expr" with "if 
(!cond) throw new AssertionError(expr)".
Then we could remove the code from all the places where we force 
assertions to be enabled for javac.
Does anyone have comments, especially any reasons why this would *not* 
be a good idea?

-- Jon