CMake: Pass build type CFLAGS to header generator.
CMake: Modify _FORTIFY_SOURCE only for release builds.

Remove build warning for Debug builds:

    # warning _FORTIFY_SOURCE requires compiling with optimization (-O)
CMake: Rename target "test" to "functionaltest".

Remove build warning:

    The target name "test" is reserved or not valid for certain CMake
    features, such as generator expressions, and may result in undefined
    behavior.
Merge pull request #1392 from fwalch/fix-build-warnings

Fix build warnings.