DCM module with internal line as CLKIN

If you get these errors:

ERROR:NgdBuild:770 - IBUFG 'Inst_DCM71/CLKIN_IBUFG_INST' and BUFG
   'Inst_DCM100/CLKFX_BUFG_INST' on net 'clk100' are lined up in series. Buffers
   of the same direction cannot be placed in series.
ERROR:NgdBuild:924 - input pad net 'clk100' is driving non-buffer primitives:

Then all you need to do is comment out the following lines from your DCM.vhdl file:

  -- CLKIN_IBUFG_INST : IBUFG
  --    port map (I=>CLKIN_IN,
  --              O=>CLKIN_IBUFG);

and replace CLKIN_IBUFG with CLK_IN in the port map, and remove the other CLKIN_IBUFG references.