And if you call init_progfile_dir(), you must call
init_process_policies() before that.
And even if you *don't* use data_file_url(), you might use it in the
future, or you might use other calls to get data file paths, so make
*all* the extcap programs make those calls.
(Yes, this is important on macOS, for example; it may also be important
on Windows. On other UN*Xes we may just compile in the data file path,
but that's not true on *all* our platforms.)
Change-Id: I99265ed69ec24096884ec067feddd7d7f3855436
Reviewed-on: https://code.wireshark.org/review/32775
Reviewed-by: Guy Harris <guy@alum.mit.edu>