Failing to do on clients was causing TLS 1.3 negotiation to fail.

Fixes bug 28245; bugfix on 0.2.9.15, when we added TLS 1.3 support.

This'll help retain test compatibility until 1.31.0 is released!

This is no longer necessary with upstream rust-lang/rust changes as well
as some local tweaks. Namely:

* The `-fsanitize=address`-style options are now passed via `-C
  link-args` through `RUSTFLAGS`. This obviates the need for the shell
  script.
* The `-C default-linker-libraries`, disabling `-nodefaultlibs`, is
  passed through `RUSTFLAGS`, which is necessary to ensure that
  `-fsanitize=address` links correctly.
* The `-C linker` option is passed to ensure we're using the same C
  compiler as normal C code, although it has a bit of hackery to only
  get the `gcc` out of `gcc -std=c99`

Closes ticket 23846

Fixes bug 27344, where we'd break compatibility with old tors by
rejecting RSA1024 and DH1024.

David Goulet authored Jul 09, 2018 and Nick Mathewson committed Aug 28, 2018

Remove support for Tor2web in the code and build system. At this commit, tor
doesn't have Tor2web support anymore.

Ref: https://lists.torproject.org/pipermail/tor-dev/2018-July/013295.html



Close #26367
Signed-off-by: David Goulet <dgoulet@torproject.org>

We used to link both libraries at once, but now that I'm working on
TLS, there's nothing left to keep OpenSSL around for when NSS is
enabled.

Note that this patch causes a couple of places that still assumed
OpenSSL to be disabled when NSS is enabled
   - tor-gencert
   - pbkdf2

I hope that the debian clang maintainers will look at debian bug
903709 soon. But until they do, this should keep our users and our
CI happy on sid with clang.

Closes ticket 26779.

If we're building for Windows, we want to use windows threads no
matter what, and we don't want to link a pthread library even if it
is present.  Fixes bug 27081; bugfix on 1790dc67 in 0.1.0.1-rc.

Based on a patch from Hello71 on ticket 20424.

This patch additionally fixes openbsd-malloc support, switches
our tcmalloc support to use pkgconfig, and tells the compiler to
omit system malloc implementations as appropriate.

squash! Add a --with-malloc option.

Edit changelog file to fix a typo and credit Alex Xu in preferred format.

Conditionalize the pragma that temporarily disables
-Wunused-const-variable.  Some versions of gcc don't support it.  We
need to do this because of an apparent bug in some libzstd headers.
Fixes bug 26785; bugfix on 0.3.2.11.

Work around two different bugs in the OS X 10.10 and later SDKs that would
prevent us from successfully targeting earlier versions of OS X.

Fixes bug 26876; bugfix on 0.3.3.1-alpha.

When it is set, include the NSS headers and libraries as
appropriate.  Doesn't actually use them yet, though.