Rawshark uses libwiretap, so it has to call wtap_init().

Change-Id: I4b87227e4828ebad98b22e5e5d1f3896e636582a
Reviewed-on: https://code.wireshark.org/review/19070
Reviewed-by: Guy Harris <guy@alum.mit.edu>

rawshark.c

@@ -514,6 +514,8 @@ main(int argc, char *argv[])
     timestamp_set_precision(TS_PREC_AUTO);
     timestamp_set_seconds_type(TS_SECONDS_DEFAULT);
 
+    wtap_init();
+
     /* Register all dissectors; we must do this before checking for the
        "-G" flag, as the "-G" flag dumps information registered by the
        dissectors, and we must do it before we read the preferences, in