merge revision(s) 6bcc4664,bb40c5cb,c060bdc2: [Backport #17541]

	Return new NODE_LIT

	As NODE_ZLIST/NODE_LIST are not markable, cannot be reused as
	NODE_LIT.
	---
	 parse.y | 7 ++-----
	 1 file changed, 2 insertions(+), 5 deletions(-)

	Ensure symbol list node is either NODE_STR or NODE_DSTR

	---
	 parse.y | 11 ++++++++---
	 1 file changed, 8 insertions(+), 3 deletions(-)

	NODE markability should not change by nd_set_type

	---
	 node.c | 31 +++++++++++++++++++++++++------
	 node.h | 12 ++++++++++++
	 2 files changed, 37 insertions(+), 6 deletions(-)