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.h b/cmds/statsd/src/DropboxReader.h
index f7d5a82..b7f8739 100644
--- a/cmds/statsd/src/DropboxReader.h
+++ b/cmds/statsd/src/DropboxReader.h
@@ -23,10 +23,13 @@
 #include <stdio.h>
 
 using android::base::unique_fd;
-using android::os::statsd::StatsLogReport;
 using android::status_t;
 using std::string;
 
+namespace android {
+namespace os {
+namespace statsd {
+
 class DropboxReader {
 public:
     // msec is the start timestamp.
@@ -42,4 +45,8 @@
     };
 };
 
+} // namespace statsd
+} // namespace os
+} // namespace android
+
 #endif //DROPBOX_READER_H