if there is an identity signaure at the end, ONLY check it if it looks
like a real one (correct magic number, cert and sig size fields are
sane etc.). this means eet opens dont fail for files that may have
trailing garbage or padding that is not an eet identity signature.
Being annoyed by different types of eina critical macros - CRI, CRIT,
CRITICAL -, I concluded to unify them to one. Discussed on IRC and
finally, CRI was chosen to meet the consistency with other macros -
ERR, WRN, INF, DBG - in terms of the number of characters.
If there is any missing bits, please let me know.