copy line/col info straight from opener/closer

We can't rely on anything in `subj` since it's been modified while parsing the
subject and could represent line info from a future line.  This is simple and
works.

Author: kivikakk

src/inlines.c

@@ -732,9 +732,10 @@ static delimiter *S_insert_emph(subject *subj, delimiter *opener,
   }
   cmark_node_insert_after(opener_inl, emph);
 
-  emph->start_line = emph->end_line = subj->line;
-  emph->start_column = opener_inl->start_column + subj->column_offset;
-  emph->end_column = closer_inl->end_column + subj->column_offset;
+  emph->start_line = opener_inl->start_line;
+  emph->end_line = closer_inl->end_line;
+  emph->start_column = opener_inl->start_column;
+  emph->end_column = closer_inl->end_column;
 
   // if opener has 0 characters, remove it and its associated inline
   if (opener_num_chars == 0) {