Removed TAG() macro and revived Tag() function for big endian platform.
Removed TAG() macro and revived Tag() function for big endian platform.

BUG=124629
TEST=ran test_{un,}malicious_fonts.sh
Review URL: https://chromiumcodereview.appspot.com/10273021
jgedler/ots,a19810227/ots,a19810227/ots,jgedler/ots,jgedler/ots,a19810227/ots