Update bucklets to latest revision

- gerrit-plugin bucklet: Fix macro resolution
- Update Buck to match version used in Gerrit
- Rename __standalone_mode__ to STANDALONE_MODE

Change-Id: I8adde95adaedbbfbcf6c68fe23e255c72e8cf998

bucklets

diff --git a/bucklets b/bucklets
index 0dbb1ae..bccbb0b 160000
--- a/bucklets
+++ b/bucklets
@@ -1 +1 @@
-Subproject commit 0dbb1ae5b35a20a849bb185fea9721fc68c3ffa4
+Subproject commit bccbb0bcb49e63cbe45bb55b7088f2bbf72b8275