gost_pmeth.c: mitigate for constness difference in copy function

The second argument for the pkey_copy function has been constified in
OpenSSL to be 3.0.  This is normally not a problem, but when passing a
pointer to such a function, the compiler does complain.

This change solves the issue by looking at the macros
OPENSSL_VERSION_MAJOR, which is new in OpenSSL to be 3.0, and set
constness based on that.

Fixes #154

travis-ci: add linux-ppc64le build

Fix test_grasshopper and test_keyexpimp engine init

Try this approach:
https://stackoverflow.com/questions/32358197/travis-ci-install-perl-module-with-non-perl-language

Make proper engine initialization for tests instead of
EVP_add_cipher/EVP_add_digest hack. Fixes #151.

travis-ci: cleanup "so/dylib" mangling, not needed

after https://github.com/openssl/openssl/pull/8951

travis-ci: add osx builds

Fix MacOS building (master branch)

Fixes #122

Не учитывается значение carry

initial cirrus-ci support

test_tls: use socketpair instead of network connection

May fix build on Cirrus-CI, issue #134.

Fix compilation on FreeBSD

Otherwise `struct sockaddr_in` is undefined for test_tls.

Reported in #123 by f-andrey.

test_digest and alignment fix for Streebog

Some architectures in some circumstances do not allow unaligned
memory access (such as ARM, MIPS) triggering SIGBUS. This patch
very crudely fixes this issue.

The issue is found and original fix is proposed by Eric Biggers:

  https://patchwork.kernel.org/patch/10878865/

Especially test alginment problems on MIPSel.

travis-ci: switch to xenial

test_tls: simple TLS connection testing

Generate cert for every parameter, set it up on s_server, connect
s_client, and transfer 1M of data to both directions.

Migrate test framework to Test2