[OTS] TAG() macro for big endian
[OTS] TAG() macro for big endian

Add TAG() macro for big endian.

BUG=chromium:124629
TEST=ran test_{un,}malicious_fonts.sh
Review URL: https://chromiumcodereview.appspot.com/10205009

irori/ots,irori/ots,khaledhosny/ots,davelab6/ots,anthrotype/ots,davelab6/ots,anthrotype/ots