[Bug #19042] Fix Dir.glob brace with '/'

	Dir.glob brace pattern with '/' after '**' does not match
	paths in recursive expansion process.
	We expand braces with '/' before expanding a recursive.

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>
	---
	 dir.c                 |  2 +-
	 test/ruby/test_dir.rb | 14 ++++++++++++++
	 2 files changed, 15 insertions(+), 1 deletion(-)