Merge pull request #240 from jwodder/lints-91

Update lints configuration

Author: jwodder

Cargo.toml

@@ -145,6 +145,7 @@ index_refutable_slice = "deny"
 infinite_loop = "deny"
 into_iter_without_iter = "deny"
 invalid_upcast_comparisons = "deny"
+ip_constant = "deny"
 items_after_statements = "deny"
 iter_filter_is_ok = "deny"
 iter_filter_is_some = "deny"
@@ -210,7 +211,6 @@ str_split_at_newline = "deny"
 string_add_assign = "deny"
 string_lit_as_bytes = "deny"
 string_lit_chars_any = "deny"
-string_to_string = "deny"
 struct_field_names = "deny"
 suboptimal_flops = "deny"
 trailing_empty_array = "deny"