Fix a regexp in depth().
Fix a regexp in depth().

The depth calculation uses a regexp that previously counted mixed header
and body symbols (e.g. "%--*--" == depth 5). It now correctly counts the
first run of contiguous symbols (e.g. "%--*--" == depth 2).

tomheon/diffscuss,hut8labs/diffscuss,tomheon/diffscuss,hut8labs/diffscuss