The new common folder holds packages and designs, which can be used
either for synthesis & simulation. The first file is UtilP.vhd, a
package containing vatious helper functions:

  * and_reduce(): function to and'ring all items of a vector, overloaded
                  for std_logic_vector & boolean_vector
  * or_reduce(): function to or'ring all items of a vector, overloaded
                 for std_logic_vector & boolean_vector
  * even_parity(): calculate the even parity of a std_logic_vector
  * odd_parity(): calculate the odd parity of a std_logic_vector