Accept both single index and range indexing in port map
Accept both single index and range indexing in port map

Currently, only a range is accepted as indexing in port map assignments. With this change, also a single index is accepted. Example:
entity comb(rtl)
    port map (i(2) => a,
              i(3) => b,
              i(1 downto 0) => c);

antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4,antlr/grammars-v4