migrate yaml lib (#130)

vendor

migrate imports

Co-authored-by: 6543 <6543@obermui.de>
Reviewed-on: https://gitea.com/gitea/tea/pulls/130
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: techknowlogick <techknowlogick@gitea.io>

vendor/gopkg.in/yaml.v2/yamlh.go

@@ -579,6 +579,7 @@ type yaml_parser_t struct {
 
 	simple_key_allowed bool                // May a simple key occur at the current position?
 	simple_keys        []yaml_simple_key_t // The stack of simple keys.
+	simple_keys_by_tok map[int]int         // possible simple_key indexes indexed by token_number
 
 	// Parser stuff