Update protobuf to fix "'HOST_CFG' is not defined"

Updating protobuf so that rougtime can be built with latest blaze

Change-Id: I461f2d685cfd11cd751f3eea5ddf31c902e89ec2

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 1d303db..6ea918a 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -8,7 +8,7 @@
 
 git_repository(
     name = "protobuf",
-    commit = "v3.0.0",
+    commit = "v3.2.0",
     remote = "https://github.com/google/protobuf",
 )