Statsd namespace is defined and used

Statsd code now lives in android::os::statsd namespace. Existing files
are largely modified to follow this convention.

Exception: parse_util, since it seems a bit different.

Test: code compiles and existing statsd_tests still pass
Change-Id: Idf92a071b9ed172d01eb3087a4fa3609d67a038c
diff --git a/cmds/statsd/src/DropboxReader.cpp b/cmds/statsd/src/DropboxReader.cpp
index cda2f43..307e771 100644
--- a/cmds/statsd/src/DropboxReader.cpp
+++ b/cmds/statsd/src/DropboxReader.cpp
@@ -23,11 +23,14 @@
 using android::String16;
 using android::binder::Status;
 using android::base::unique_fd;
-using android::os::statsd::EventMetricData;
 using android::os::DropBoxManager;
 using android::ZipUtils;
 using std::vector;
 
+namespace android {
+namespace os {
+namespace statsd {
+
 status_t DropboxReader::readStatsLogs(FILE* out, const string& tag, long msec) {
     sp<DropBoxManager> dropbox = new DropBoxManager();
     StatsLogReport logReport;
@@ -117,3 +120,7 @@
     }
     fprintf(out, "\n");
 }
+
+} // namespace statsd
+} // namespace os
+} // namespace android