dillon1000/react

MergeConsecutiveBlocks traverses function expressions

Currently the process of lowering function expression bodies is deferred until 
AnalyzeFunctions. However, per the motivation of the previous PR, we'd like to 
be able to perform inference across function expression boundaries. To do that 
we need to use consistent identifier ids across function expression boundaries. 
This requires SSA conversion of function expressions at the same time as we 
enter SSA. 

To start, this PR moves MergeConsecutiveBlocks for function expressions into 
that phase.