Handle abnormal exit of s_client/s_server processes.

Fixes partially #230.

Support of pkeyutl -pkeyopt ukmhex:0102030405060708 syntax

There need to be more tests than 2 constant fixed size blocks.
Final digest values are generated from the first run.

Test description in comments.

Plus some minor chnages
- function defenition doen't match function declaration
- Consecutive break statement is unnecessary.
- Type missmatch in format string