expose pick-an-integer

Exposed pick-an-integer and wrote tests for it, oops.

# Please enter the commit message for your changes. Lines starting
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# Author:    Mongoose <synx@synx.us.to>
# Committer: synx <synx@synx.us.to>
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#	modified:   main.ss
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#	info.ss~
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#	sizeof.plt
#	test-sizeof.ss~