Remove use of unsigned char in table_lookup().
Remove use of unsigned char in table_lookup().

eddieantonio/isri-ocr-evaluation-tools,eddieantonio/isri-ocr-evaluation-tools,eddieantonio/isri-ocr-evaluation-tools,eddieantonio/ocreval,eddieantonio/ocreval,eddieantonio/ocreval