Merge pull request #3 from dkg/master

API pruning
removed init/deinit function declarations
fixed indentation
removed unused variable 'it'
new function psl_registered_domain()
added reference to Gmane mailing list archive
added psl_registrable_domain(), renamed psl_registered_domain -> psl_unregistrable_domain
fixed punycode sorting
skip 'example' unregistered TLD tests, added some special tests
added test_psl.txt so satisfy distcheck
change psl_free() to take a psl_ctx_t *psl

This uses the more common convention where the variable freed is the
thing returned from the constructor directly, rather than having the
deallocator also zero out the pointer itself.
added utf-8 to lowercase code using sed
prevailing rule is *
finished comment
check input params in exported functions
removed fprintf from library code
lowercase libpsl in AC_INIT
own line for mailing list reference
fixed errors introduced in last change
removed incomplete and unneeded initialization of _builtin_psl