config/Block: add method SetUsed()

src/config/Block.hxx

@@ -94,6 +94,10 @@ struct ConfigBlock {
 		return block_params.empty();
 	}
 
+	void SetUsed() const noexcept {
+		used = true;
+	}
+
 	template<typename N, typename V>
 	gcc_nonnull_all
 	void AddBlockParam(N &&_name, V &&_value, int _line=-1) noexcept {

src/config/Global.cxx

@@ -85,7 +85,7 @@ config_get_block(ConfigBlockOption option) noexcept
 {
 	const auto *block = config_data.blocks[unsigned(option)];
 	if (block != nullptr)
-		block->used = true;
+		block->SetUsed();
 	return block;
 }