fprintf/vfprintf dependency fix

fprintf/vfprintf dependency fix

* src/vm/os.hpp: Added vfprintf wrapper
                 removed fprintf wrapper, but kept the availability check
* configure.ac: Added vfprintf linker check
* src/toolbox/logging.cpp: using os::vfprintf
* src/vm/vm.cpp: version

Due to a compatibility check of clang 2.7, the decision was made to define that fprintf is mandatory for cacao