tools/obu_parser.cc: make some functions static

Fixes some -Wmissing-prototypes warnings.

Bug: aomedia:3416
Change-Id: Ia0f3b9cf38598b785c692f0a0c8c97cd2df71c0c

tools/obu_parser.cc

diff --git a/tools/obu_parser.cc b/tools/obu_parser.cc
index 5716b46..4053615 100644
--- a/tools/obu_parser.cc
+++ b/tools/obu_parser.cc
@@ -20,6 +20,7 @@
 #include "tools/obu_parser.h"
 
 namespace aom_tools {
+namespace {
 
 // Basic OBU syntax
 // 8 bits: Header
@@ -116,6 +117,8 @@
   }
 }
 
+}  // namespace
+
 bool DumpObu(const uint8_t *data, int length, int *obu_overhead_bytes) {
   const int kObuHeaderSizeBytes = 1;
   const int kMinimumBytesRequired = 1 + kObuHeaderSizeBytes;