build: improve csv process CMake and C compatibility
- Add
CSV_PROCESS_TEST_DIRcompile definition for test configuration. - Expose
CSV_PROCESS_TEST_DIRthrough the test preprocessing definitions. - Disable CMake lint line-length warning for the project declaration.
- Add
extern "C"guards to the C implementation and demo sources for C++ compatibility. - Display CSV process version information in the demo executable.
- Include
version.hin the demo for build-time version reporting.