Fix to prevent segfaults when the last audio frame is truncated.
When the last audio frame is truncated, "mp3check --cut-junk-end" fails to
detect and get rid of it.
.
In the best case scenario, when the mp3 file has no id3 tag, the corrupted
frame is left as is.
.
In the worst case scenario, when the frame is followed by id3 tags, the frame
is considered as complete and the tags are restored beyond the end of the
memory-mapped file, which may cause a segmentation fault.
.
This patch aims to detect and eliminate any truncated last audio frame when
mp3check is called with the --cut-junk-end option.
