don't call load_pokecrystal_macros 2000 times

Also, don't call make_macro_table 2000 times by only calling it once and
passing the result.
reset stdout in prequeue.py near end

Other output shouldn't be dumped into items/item_attributes.tx by
default.
better read_line performance in preprocessor

Jump out of read_line early if the line is an empty string or a newline.
even better performance for read_line
give preprocessor.py a main()
Merge pull request #185 from kanzure/preprocessor-performance

Preprocessor performance improvements.

This recliams 0.4 seconds.