merge revision(s) 5bc8fceca8d47ed1ef9c603c6531a408de36b60c: [Backport #19835]

	Fix memory leak in parser for incomplete tokens

	[Bug #19835]

	The parser does not free the `tbl` of the `struct vtable` when there are
	leftover `lvtbl` in the parser. This causes a memory leak.

	The following script reproduces this issue:

	```
	10.times do
	  100_000.times do
	    Ripper.parse("class Foo")
	  end

	  puts `ps -o rss= -p #{$$}`
	end
	```
	---
	 parse.y                    | 42 ++++++++++++++++++++++++++++--------------
	 test/ripper/test_ripper.rb |  7 +++++++
	 2 files changed, 35 insertions(+), 14 deletions(-)

0 files changed, 0 insertions, 0 deletions