Include testbed for simulation in GHDL.

Include testbed for simulation in GHDL.

Some top level attributes required for safe build for real hardware
with asynchronous external access has to be disabled for GHDL simulation.

 	-- XST attributes
 	attribute REGISTER_DUPLICATION : string;
-	attribute REGISTER_DUPLICATION of rd : signal is "NO";
+	--attribute REGISTER_DUPLICATION of rd : signal is "NO";
 	attribute REGISTER_DUPLICATION of rd_f_s : signal is "NO";
-	attribute REGISTER_DUPLICATION of bls : signal is "NO";
+	--attribute REGISTER_DUPLICATION of bls : signal is "NO";
 	attribute REGISTER_DUPLICATION of bls_f_s : signal is "NO";
-	attribute REGISTER_DUPLICATION of address : signal is "NO";
+	--attribute REGISTER_DUPLICATION of address : signal is "NO";
 	attribute REGISTER_DUPLICATION of address_f_s : signal is "NO";
-	attribute REGISTER_DUPLICATION of cs0_xc : signal is "NO";
+	--attribute REGISTER_DUPLICATION of cs0_xc : signal is "NO";
 	attribute REGISTER_DUPLICATION of cs0_xc_f_s : signal is "NO";

 	-- XST attributes
 	attribute REGISTER_DUPLICATION : string;
-	attribute REGISTER_DUPLICATION of rd : signal is "NO";
+	--attribute REGISTER_DUPLICATION of rd : signal is "NO";
 	attribute REGISTER_DUPLICATION of rd_f_s : signal is "NO";
-	attribute REGISTER_DUPLICATION of bls : signal is "NO";
+	--attribute REGISTER_DUPLICATION of bls : signal is "NO";
 	attribute REGISTER_DUPLICATION of bls_f_s : signal is "NO";
-	attribute REGISTER_DUPLICATION of address : signal is "NO";
+	--attribute REGISTER_DUPLICATION of address : signal is "NO";
 	attribute REGISTER_DUPLICATION of address_f_s : signal is "NO";
-	attribute REGISTER_DUPLICATION of cs0_xc : signal is "NO";
+	--attribute REGISTER_DUPLICATION of cs0_xc : signal is "NO";
 	attribute REGISTER_DUPLICATION of cs0_xc_f_s : signal is "NO";

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>