Update usage information on local_dc.

src/local_dc/local_dc.c

@@ -446,7 +446,7 @@ int __CDECL
                          's',
                          ARGS_NO_LONG,
                          "systems",
-                         "Space seperated list of systems.",
+                         "Space seperated list of systems (conflicts with --systab).",
                          &sysname_,
                          "" );
     args_add_string_ptr(
@@ -454,7 +454,7 @@ int __CDECL
         ARGS_NO_SHORT,
         "systab",
         "systab file",
-        "Read the model list from the given systab file (overrides -s).",
+        "Read the model list from the given systab file (conflicts with -s).",
         &systab_fname,
         "" );
     args_add_string_ptr( arg_parser,