Consolidate namespace for using GFlags.

Summary:
Default namespace for GFlags has been changed from "google" to "gflags".

See: https://github.com/gflags/gflags/commit/d9d06b9.
Closes https://github.com/facebook/folly/pull/466

Reviewed By: yfeldblum

Differential Revision: D3787144

Pulled By: Orvid

fbshipit-source-id: db7bcaf4e2bcd46b022a48b17b50ef155570f296

folly/init/Init.cpp

@@ -39,7 +39,7 @@ void init(int* argc, char*** argv, bool removeFlags) {
   google::InstallFailureSignalHandler();
 #endif
 
-  google::ParseCommandLineFlags(argc, argv, removeFlags);
+  gflags::ParseCommandLineFlags(argc, argv, removeFlags);
 
   auto programName = argc && argv && *argc > 0 ? (*argv)[0] : "unknown";
   google::InitGoogleLogging(programName);

folly/test/AtomicUnorderedMapTest.cpp

@@ -397,7 +397,7 @@ BENCHMARK(fast_map_64) {
 
 int main(int argc, char ** argv) {
   testing::InitGoogleTest(&argc, argv);
-  google::ParseCommandLineFlags(&argc, &argv, true);
+  gflags::ParseCommandLineFlags(&argc, &argv, true);
   int rv = RUN_ALL_TESTS();
   folly::runBenchmarksOnFlag();
   return rv;

folly/test/SparseByteSetBench.cpp

@@ -151,7 +151,7 @@ void setup_rand_bench() {
 }
 
 int main(int argc, char** argv) {
-  google::ParseCommandLineFlags(&argc, &argv, true);
+  gflags::ParseCommandLineFlags(&argc, &argv, true);
   setup_rand_bench();
   runBenchmarks();
   return 0;