initial draft of optimizer, inactive ATM.
working build, lots of debug output, more intelligence.
nqp-jvm doesn't like negative nums in substr
this should have been gone already.
little improvements. actually finds symbols now.
removed debug output
Merge branch 'origin/nqp-optimizer'

This gives us an optimizer for NQP that removes some int to num and
num to int coercions if they are superfluous.