Add suppressions for memcheck errors.

tools/valgrind-webrtc/memcheck/suppressions.txt

Index: tools/valgrind-webrtc/memcheck/suppressions.txt
diff --git a/tools/valgrind-webrtc/memcheck/suppressions.txt b/tools/valgrind-webrtc/memcheck/suppressions.txt
index cea759b52a9f2bd6fdd809a05e330faf89022347..c3130244cf9a36374515ff75c1a43238c8c1192f 100644
--- a/tools/valgrind-webrtc/memcheck/suppressions.txt
+++ b/tools/valgrind-webrtc/memcheck/suppressions.txt
@@ -441,3 +441,39 @@
    fun:_ZN6webrtc15GainControlImpl19ProcessCaptureAudioEPNS_11AudioBufferEb
    ...
 }
+{
+   bug_5986
+   Memcheck:Unaddressable
+   fun:silk_stereo_LR_to_MS
+   fun:silk_Encode
+   fun:opus_encode_native
+   ...
+}
+{
+   bug_5987
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN6webrtc51AudioEncoderCopyRedDeathTest_NullSpeechEncoder_Test8TestBodyEv
+}
+{
+   bug_5988
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZNSt8_Rb_treeISsSt4pairIKSsSsESt10_Select1stIS2_EN3rtc5ilessESaIS2_EE15_M_insert_equalIS2_EESt17_Rb_tree_iteratorIS2_EOT_
+   fun:_ZN3rtc8HttpData12changeHeaderERKSsS2_NS0_13HeaderCombineE
+   fun:_ZN3rtc16HttpResponseData9set_errorEj
+   fun:_ZN3rtc12_GLOBAL__N_117HttpServerMonitor9OnRequestEPNS_10HttpServerEPNS_21HttpServerTransactionE
+   fun:_ZN3rtc10HttpServer10Connection14onHttpCompleteENS_8HttpModeENS_9HttpErrorE
+   fun:_ZN3rtc8HttpBase10OnCompleteENS_9HttpErrorE
+   fun:_ZN3rtc8HttpBase17OnHttpStreamEventEPNS_15StreamInterfaceEii
+   fun:_ZN7testing12StreamSource11QueueStringEPKc
+   fun:_ZN3rtc12_GLOBAL__N_122CreateClientConnectionERNS_10HttpServerERNS0_17HttpServerMonitorEb
+   fun:_ZN3rtc47HttpServer_SignalsCloseAfterForcedCloseAll_Test8TestBodyEv
+}
+{
+   bug_5989
+   Memcheck:Unaddressable
+   ...
+   fun:_ZNK3rtc15CriticalSection5EnterEv
+   ...
+}