#2 Check return codes everywhere

[Markus Elfring]

Some checks for return codes are missing.

Examples:
Would you like to add more error handling for return values from "ftell" like in the function "open_tta_file" and from "fseek" in the function "read_id3_tags"?
http://tta.cvs.sourceforge.net/tta/ttalib-hwplayer/ttadec.c?revision=1.2&view=markup