wcap-decode: free malloc'd frame variable

The 'frame' variable does not appear to be used for anything
useful and is probably dead code... perhaps we should just remove
it.

Nonetheless, at least free it at the end of the program.

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
wcap-decode: check for NULL results

Check for malloc failures and failed wcap_decoder_create.
Print context messages to stderr when things fail.

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
wcap-decode: remove dead code

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>