Added posix clock.c
Added posix clock.c

pacheco017/libcsp,Psykar/kubos,GomSpace/libcsp,Psykar/kubos,pacheco017/libcsp,GomSpace/libcsp,kubostech/KubOS,satlab/libcsp,Psykar/kubos,satlab/libcsp,kubostech/KubOS,Psykar/kubos,satlab/libcsp,Psykar/kubos,Psykar/kubos,libcsp/libcsp,GomSpace/libcsp,libcsp/libcsp,pacheco017/libcsp,pacheco017/libcsp,Psykar/kubos