GTest translation for C is not very good

[emilybache]

Many of the teams I coach in C use googletest, so it seemed like a good idea to have gtest as an alternative to cmocka. So I had a go at a translation, and put it in the subfolder 'c_gtest'. Unfortunately my skills with C and gtest and CMake are really not up to it, and there is a lot of duplication in the test code, and if we're honest, more than's necessary in the production code header files. Anyway I thought I'd put it out there as an issue in case there's anyone who would like to improve on my attempts and send me a pull request :-)