Do various minor dissector changes:

- remove unneeded initializers;
- replace tabs in files with editor mode line 'expandtabs';
- col_set_str() --> col_add_str() (in one case);
- tvb_length() -- > tvb_reported_length() (in one case);
- do some whitespace & indentation fixes/changes.

Change-Id: Ib8ffbbcdb6e4a74c0df6021a75430ae1ef9ae089
Reviewed-on: https://code.wireshark.org/review/3435
Reviewed-by: Bill Meier <wmeier@newsguy.com>