Make protobuf build

This includes the following:
  - Setting up dependencies protobuf needs
  - A few hacks to make protobuf work with our version of Bazel (going
    to upgrade soon...)
  - A few tweaks to make protobuf be happy in third_party
  - Commenting out a few things we don't care about that didn't want to
    work

Tested with -c fastbuild for all 3 toolchains.

Change-Id: I02c50cd7e82e509bd7973f2e7cecf9b7d183783e
diff --git a/third_party/googletest/BUILD b/third_party/googletest/BUILD
index f342e66..fcec287 100644
--- a/third_party/googletest/BUILD
+++ b/third_party/googletest/BUILD
@@ -95,6 +95,15 @@
 )
 
 cc_library(
+    name = "googlemock_main",
+    visibility = ["//visibility:public"],
+    deps = [
+        ":googlemock",
+        ":googletest_main",
+    ],
+)
+
+cc_library(
 	name = "googletest_sample_libs",
 	hdrs = [
 	    "googletest/samples/prime_tables.h",