Fix bug with CMake project variable

Fix bug with CMake project variable

"
I tried to embed the check source code into my project in a "3rdparty" folder. Turns out that the build fails because of the usage of CMAKE_PROJECT_NAME instead of PROJECT_NAME in the check CMakeLists.txt

CMAKE_PROJECT_NAME is the name of the topmost project, that is in my case my own project.
Changing to PROJECT_NAME worked fine.
"

https://github.com/libcheck/check/issues/194

Signed-off-by: Mikko Johannes Koivunalho <mikko.koivunalho@iki.fi>