Various changes for DMG. Avoid false positives. Hopefully we're not
introducing false negatives (None of our sample hashes produce any)
because now we're only checking for eight consecutive nulls, either
in main blob or secondary one.
Merge pull request #522 from magnumripper/dmg-null

Proposed changes for DMG
wpapcap2john: Add some sanity checks. Closes #518.
Also cosmetical fixes (license, whitespace) in WPA source files.
hccap2john: Add same extra output that was recently added to wpapcap2john
(BSSID's, filename etc) and handle multiple files better (don't abort on
error, print filename among warnings). Closes #521.
Also, support multiple entries in each file. This was a weird
limitation but it might have been due to Hashcat legacy behavior (it
initially only supported one per file). Anyways it's lifted now.
wpapcap2john: Add support for Radiotap encapsulation. Closes #377.
wpapcap2john: Add support for Prism & PPI encapsulations.
wpapcap2john: Add a note in output about unsure authentications
(still crackable but might be an incorrect password for that AP).
Closes #519.
Cherry-pick 2475121 from Dhiru - Travis/Coverity support. Closes #512.
White space fixes (fixing over-long lines) in core files.
"Secure Mode" implemented. When this is enabled in john.conf, no
cracked password is ever printed, logged or stored in plaintext.
Instead you get an indication of length and use of classes. For
example, the password "Ignit3" would output as L6-?l?d?u telling
you that it's six characters long and consists of lowercase, digits
and uppercase characters.  This closes #505.
LUKS fixes (format change!)