ari: Fix generators for resources with camelCase names.

For the new deviceState resource, we need to properly generate
device_state.[ch] files.
........

Merged revisions 402981 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@402982 f38db490-d61c-443f-a65b-d21fe96a405b