Added ddr technology library for both DDR3 and DDR4

libraries/technology/ddr/hdllib.cfg

+hdl_lib_name = tech_ddr
+hdl_library_clause_name = tech_ddr_lib
+hdl_lib_uses = common
+hdl_lib_technology = 
+
+build_dir_sim = $HDL_BUILD_DIR
+build_dir_synth = $HDL_BUILD_DIR
+
+synth_files =
+    tech_ddr_pkg.vhd
+
+test_bench_files =