libs3: dist and distdir make targets

Signed-off-by: Sage Weil <sage@inktank.com>

diff --git a/src/libs3 b/src/libs3
index 2f92edd36f73de558957909a0b90af9f755be59c..f049cb9840b38e96cb76f78242f067c154d1c666 160000 (submodule)
--- a/src/libs3
+++ b/src/libs3
@@ -1 +1 @@
-Subproject commit 2f92edd36f73de558957909a0b90af9f755be59c
+Subproject commit f049cb9840b38e96cb76f78242f067c154d1c666