This patch wraps GetProcAddress into a C++ template to make it easier to
use and to allow us to ignore the cast-function-type warning in a
central location.
It also simplifies a lot of the uses due to template argument deduction
and changes winapi.cc to use macros that reduce repetition.

Disable maybe-uninitialized warning that may occur when building with
sanitizers enabled.

Introduce a macro to allow calling deprecated OpenSSL functionality,
mostly the old non-EVP interfaces.
Also allow calling EVP_md5() which is deprecated on Solaris only, so can
also re-enable the deprecated-declarations warning on Solaris, too.

and fix some issues in droplet_device

When initializing PyTypeObject, there are a lot of fields to set. To
avoid problems due to mis-ordering, we change this to use designated
inizializers. While these are not legal in C++17, they're in C99,
available as a compiler extension on virtually any major compiler and
will became legal in C++20.

as this is C code, we cannot use [[fallthrough]] (yet).

in FreeTree() we kept the count of free'd blocks for a Dmsg. However
Dmsgs are disabled in tree.cc, so it was never used.

Instead of two similar functions we now have one that takes parameters.