Added some stuff from modem and added formal

cores/util/cdc/cdc.core

@@ -0,0 +1,16 @@
+CAPI=2:
+
+name: joppeb:util:cdc:1.0
+description: Clock-domain crossing helpers
+
+filesets:
+    rtl:
+        files:
+            - rtl/cdc_strobe_data.v
+            - rtl/cdc_req_resp.v
+        file_type: verilogSource
+
+targets:
+    default:
+        filesets:
+            - rtl