Use Cmake for fuzzing.

Some files, e.g. encode_accessors.c, use loop initial declarations
that are only allowed in C99 mode. Newer compilers enable that mode
automatically, but olders might fail. CMAKE_C_STANDARD got add in
CMake-3.1, so let's increase the minimal version by 0.1.
Signed-off-by: Christoph Junghans <junghans@votca.org>

Found by libFuzzer

Follow shared library standard: libXXX.so now gets symlinked
libXXX.so.2, which is symlinked to the real library libXXX.so.X.Y.Z
Signed-off-by: Christoph Junghans <junghans@votca.org>

Follow GNU convention for install directories, especially using
`lib64` instead of `lib`.
Signed-off-by: Christoph Junghans <junghans@votca.org>