openssl-enc: Support recent OpenSSL's encrypted files, or at least refuse to work on them

Well, # 4414 shows us that a commit with untested code was merged. So, I:

$ openssl aes-256-cbc -a -salt -in 4414.patch -out secrets.txt.enc

And I noticed that in addition to dozens of false positives per second, the correct password was not found.

$ john teste --mask=openw?a?ll
Note: This format may emit false positives, so it will keep trying even after finding a
possible candidate.
Using default input encoding: UTF-8
Loaded 1 password hash (openssl-enc, OpenSSL "enc" encryption [32/64])
Warning: poor OpenMP scalability for this hash type, consider --fork=8
Will run 8 OpenMP threads
Press 'q' or Ctrl-C to abort, almost any other key for status
openw%nl         (secrets.txt.enc)
openw+rl         (secrets.txt.enc)
openw~sl         (secrets.txt.enc)
openw)ml         (secrets.txt.enc)
openwrbl         (secrets.txt.enc)
openwUvl         (secrets.txt.enc)
openw6fl         (secrets.txt.enc)
openwzxl         (secrets.txt.enc)
8g 0:00:00:00 N/A 25.00g/s 7718p/s 7718c/s 7718C/s openw!fl..openw|ql
Session completed. 

Start by reproducing the reported openssl-enc case with the shown openssl aes-256-cbc command and John the Ripper mask. Trace how the openssl-enc format handles recent OpenSSL encrypted files; done means the correct password is found without false positives, or the unsupported files are rejected clearly.