Add ERROR and OK constants
gunzip_and_replace returns 0 for success
update_country_database returns 0 on success
update_database_general returns 0 on success
update_database_general_all returns 0 on success
The exit code is 1 whenever one of the updates fail
Add missing return code in gunzip_and_replace
Make more functions static
Continue with the next db even if we can't update the current database.
Cosmetic changes
Merge pull request #6 from maxmind/bz/cont-on-error

Bz/cont on error