benchmark: Extend sign/verify benchmark.

- Cycle through all supported parameters.
- Also do verification tests.
- Increase precision of timer (allow test to work faster).

benchmark is done separately.

Split and integrate tests

Move test code from gost_keyexpimp.c into separate test_keyexpimp.c and
link into test target.

Also, make tests work without requiring config.

Add LICENSE file to satisfy the lawyer in you

Cmake improvements

The directory can be overriden by setting the CMake variable OPENSSL_ENGINES_DIR

CMakeLists.txt uses `add_test` to execute `test/run_tests` which does the same thing as the `prove` line did.

GOST 28147-89 test suite from
https://github.com/openssl/openssl/blob/26906f2d93ad4bc092b8b5783d1b35f8c9f0c6d8/engines/ccgost/gost2814789t.c
WIP

Test to validate curve parameters

NID_id_tc26_gost_3410_2012_256_paramSetA
NID_id_tc26_gost_3410_2012_512_paramSetC

test_context: make tests return values affect overall test result

In-place encryption tests and fixes

Currently, for Grasshopper only.