Add CRC32 test basing on Google Test Framework

So far there were no unit-tests for the code. Herein is the proposal. 

Test structure is intended to resemble hierarchical structure of code that is supposed to be tested. Each source file of code to be tested  has  associated  dedicated directory  within  which test implementation and related data should be contained

Such structure produces separate testing executable for each source file  that enables in future selective triggering of unit tests basing on git report of files that were changed in particular commit (git show --pretty="format:" --name-only HEAD)