Fix lowercase table initialization (bug 1221)

The for loop needed to check for < 256, not < 255.

Fix for bug 1221 (https://redmine.openinfosecfoundation.org/issues/1221)

Passes PR script:

https://buildbot.suricata-ids.org/builders/ken-tilera/builds/138
https://buildbot.suricata-ids.org/builders/ken-tilera-pcap/builds/72