Add coverage for Parrot_register_string and Parrot_unregister_string
Add coverage for Parrot_register_string and Parrot_unregister_string

FROGGS/parrot,parrot/parrot,tkob/parrot,tkob/parrot,FROGGS/parrot,tkob/parrot,gagern/parrot,gitster/parrot,FROGGS/parrot,gagern/parrot,youprofit/parrot,tkob/parrot,gagern/parrot,gagern/parrot,gagern/parrot,parrot/parrot,parrot/parrot,gitster/parrot,youprofit/parrot,FROGGS/parrot,youprofit/parrot,gitster/parrot,gitster/parrot,tkob/parrot,youprofit/parrot,FROGGS/parrot,FROGGS/parrot,youprofit/parrot,FROGGS/parrot,youprofit/parrot,parrot/parrot,gagern/parrot,youprofit/parrot,youprofit/parrot,tkob/parrot,gitster/parrot,parrot/parrot,gitster/parrot,gitster/parrot,tkob/parrot,gagern/parrot,tkob/parrot,FROGGS/parrot