Nobody but Tor uses certs on the wire with 2 hour lifetimes,
and it makes us stand out. Resolves ticket 4014.

Using strncpy meant that if listenaddress were ever >=
sizeof(sockaddr_un.sun_path), we would fail to nul-terminate
sun_path.  This isn't a big deal: we never read sun_path, and the
kernel is smart enough to reject the sockaddr_un if it isn't
nul-terminated.  Nonetheless, it's a dumb failure mode.  Instead, we
should reject addresses that don't fit in sockaddr_un.sun_path.

Coverity found this; it's CID 428.  Bugfix on 0.2.0.3-alpha.

When we rejected a descriptor for not being the one we wanted, we
were letting the parsed descriptor go out of scope.

Found by Coverity; CID # 30.

Bugfix on 0.2.1.26.

(No changes file yet, since this is not in any 0.2.1.x release.)

I'm not one to insist on C's miserly stack limits, but allocating a
256K array on the stack is too much even for me.

Bugfix on 0.2.1.7-alpha.  Found by coverity.  Fixes CID # 450.

We had all the code in place to handle this right... except that we
were unconditionally opening a PF_INET socket instead of looking at
sa_family.  Ow.

Fixes bug 2574; not a bugfix on any particular version, since this
never worked before.

Rename crypto_pk_check_key_public_exponent to crypto_pk_public_exponent_ok:
it's nice to name predicates s.t. you can tell how to interpret true
and false.

The new behavior is to try to rename the old file if there is one there
that we can't read.  In all likelihood, that will fail too, but at least
we tried, and at least it won't crash.

Here I looked at the results of the automated conversion and cleaned
them up as follows:

   If there was a tor_memcmp or tor_memeq that was in fact "safe"[*] I
   changed it to a fast_memcmp or fast_memeq.

   Otherwise if there was a tor_memcmp that could turn into a
   tor_memneq or tor_memeq, I converted it.

This wants close attention.

[*] I'm erring on the side of caution here, and leaving some things
as tor_memcmp that could in my opinion use the data-dependent
fast_memcmp variant.

This commit is _exactly_ the result of

perl -i -pe 's/\bmemcmp\(/tor_memcmp\(/g' src/*/*.[ch]
perl -i -pe 's/\!\s*tor_memcmp\(/tor_memeq\(/g' src/*/*.[ch]
perl -i -pe 's/0\s*==\s*tor_memcmp\(/tor_memeq\(/g' src/*/*.[ch]
perl -i -pe 's/0\s*!=\s*tor_memcmp\(/tor_memneq\(/g' src/*/*.[ch]
git checkout src/common/di_ops.[ch]
git checkout src/or/test.c
git checkout src/common/test.h

The tor_memcmp code is by Robert Ransom, and the tor_memeq code is
by me.  Both incorporate some ideas from DJB's stuff.