Fixed recursive brace expansion

https://github.com/fish-shell/fish-shell/issues/399

tests/test1.in

@@ -10,6 +10,11 @@ for i in 1 2 #Comment on same line as command
 	end;
 end
 
+# Bracket expansion
+echo x-{1}
+echo x-{1,2}
+echo foo-{1,2{3,4}}
+
 # Simple alias tests
 
 function foo

tests/test1.out

@@ -2,6 +2,9 @@
 1b
 2a
 2b
+x-1
+x-1 x-2
+foo-1 foo-23 foo-24
 Test 2 pass
 Test  pass
 Test 3 pass