EXPPP: output schema should match input schema

This will close #244 

* don't replace 'DIV' with '/' (01f6e26)
* aggregate initializers with repeat now work (263fcf1b9e, a75668e31, 7cad4abf6c)
* EXPRESS sci notation requires a decimal point (a3d5343) **(not completely fixed yet)**
  * some precision is lost, and I'm not yet sure how to fix this. I'm not sure if it is worse than before or not. 

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Minor changes:
* remove exptoks.h
* fix some warnings
* rename index_spec and limit_spec to bound_spec in expparse.y, to match the part 11 BNF
* replace all LISTadd with LISTadd_last, eliminate the LISTadd macro