dir.c: fix Dir.glob with braces and matching dir

	* dir.c (join_path_from_pattern): add the last slash for directory
	  matching.

	* test/ruby/test_dir.rb (test_glob_recursive_directory): add a test
	  for above.
	  [ruby-core:91110] [Bug #15540]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_6@66848 b2dd03c8-39d4-4d8f-98ff-823fe69b080e