Fix bugs found by Coverity in decryptcore(8) and savecore(8):

• Perform final decryption and write decrypted data in case of non-block aligned

input data;

• Use strlcpy(3) instead of strncpy(3) to verify if paths aren't too long;
• Check errno after calling unlink(2) instead of calling stat(2) in order to

verify if a decrypted core was created by a child process;

• Free dumpkey.

Reported by: Coverity, cem, pfg
Suggested by: cem
CID: 1366936, 1366942, 1366951, 1366952
Approved by: pjd (mentor)