crc: basic CMake support

[VShilenkov]

supports CMake
build, install, test routines available
generate cmake configuration for find_package()
generate pkg_config instructions

supports include_what_you_use, clang-tidy, unit testing, generation of examples, code coverage report

[lammertb]

Thanks for the pull request.

Can you explain to me what these more than 1300 undocumented lines add to the functionality of the CRC calculations?

[VShilenkov]

Code of the project ( sources and headers) was untouched. So it doesn't affect functionality.
This PR allows all who uses CMake include libcrc to the project in a straightforward way.
Also for those who rely on pkg_config ways of resolving dependencies

[lammertb]

So it doesn't add functionality to the CRC functionality, only functionality for project management.
And to be honest, I don't like undocumented code.

Without documentation, this PR will not be merged.

[VShilenkov]

cmake lists has inline comments which describes sections and purpose of each block
give me an example of how would you like this files to be documented and I will work on that

[lammertb]

It should basically cover the following points

• What it does in a broad sense
• How it functions internally
• How it should be invoked
• If the code is auto-generated or manually coded
• If it is auto-generated, which tools and settings were used
• If it is a derived work or original work
• The license under which the derived or original work is released

[lammertb]

As an addition: please also look at the INSTALL file in https://github.com/lammertb/libcrc/blob/master/INSTALL which details the specific reasons why the old-fashioned make tool was used in the package, rather than cmake.

[VShilenkov]

• in a broad sense it provides CMake support, which gives everything that it usually gives: build, test, install, config for CMake projects
• provides developer options: build and run tests, build and run examples, collect code coverage, verify with static code analysis like clang-tidy,
• About internal functions: all CMake modules are now documented with the standard documentation way for CMake scripts
• On how to invoke: described in INSTALL file
• It is manually coded, no tools used
• it is part of the collection of cmake scripts that I wrote during my previous work, it is not published yet
• some files are marked with license now