modules: more interface -> include renames

This changes the following module directories:
* webrtc/modules/audio_conference_mixer/interface
* webrtc/modules/interface
* webrtc/modules/media_file/interface
* webrtc/modules/rtp_rtcp/interface
* webrtc/modules/utility/interface

To avoid breaking downstream, I followed this recipe:
1. Copy the interface dir to a new sibling directory: include
2. Update the header guards in the include directory to match the style guide.
3. Update the header guards in the interface directory to match the ones in include. This is required to avoid getting redefinitions in the not-yet-updated downstream code.
4. Add a pragma warning in the header files in the interface dir. Example:
#pragma message("WARNING: webrtc/modules/interface is DEPRECATED; "
                "use webrtc/modules/include")
5. Search for all source references to webrtc/modules/interface and update them to webrtc/modules/include (*.c*,*.h,*.mm,*.S)
6. Update all GYP+GN files. This required manual inspection since many subdirectories of webrtc/modules referenced the interface dir using ../interface etc(*.gyp*,*.gn*)

BUG=5095
TESTED=Passing compile-trybots with --clobber flag:
git cl try --clobber --bot=win_compile_rel --bot=linux_compile_rel --bot=android_compile_rel --bot=mac_compile_rel --bot=ios_rel -m tryserver.webrtc

R=stefan@webrtc.org, tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1417683006 .

Cr-Commit-Position: refs/heads/master@{#10500}
diff --git a/webrtc/modules/utility/include/process_thread.h b/webrtc/modules/utility/include/process_thread.h
new file mode 100644
index 0000000..285a5ea
--- /dev/null
+++ b/webrtc/modules/utility/include/process_thread.h
@@ -0,0 +1,66 @@
+/*
+ *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_UTILITY_INCLUDE_PROCESS_THREAD_H_
+#define WEBRTC_MODULES_UTILITY_INCLUDE_PROCESS_THREAD_H_
+
+#include "webrtc/typedefs.h"
+#include "webrtc/base/scoped_ptr.h"
+
+namespace webrtc {
+class Module;
+
+class ProcessTask {
+ public:
+  ProcessTask() {}
+  virtual ~ProcessTask() {}
+
+  virtual void Run() = 0;
+};
+
+class ProcessThread {
+ public:
+  virtual ~ProcessThread();
+
+  static rtc::scoped_ptr<ProcessThread> Create(const char* thread_name);
+
+  // Starts the worker thread.  Must be called from the construction thread.
+  virtual void Start() = 0;
+
+  // Stops the worker thread.  Must be called from the construction thread.
+  virtual void Stop() = 0;
+
+  // Wakes the thread up to give a module a chance to do processing right
+  // away.  This causes the worker thread to wake up and requery the specified
+  // module for when it should be called back. (Typically the module should
+  // return 0 from TimeUntilNextProcess on the worker thread at that point).
+  // Can be called on any thread.
+  virtual void WakeUp(Module* module) = 0;
+
+  // Queues a task object to run on the worker thread.  Ownership of the
+  // task object is transferred to the ProcessThread and the object will
+  // either be deleted after running on the worker thread, or on the
+  // construction thread of the ProcessThread instance, if the task did not
+  // get a chance to run (e.g. posting the task while shutting down or when
+  // the thread never runs).
+  virtual void PostTask(rtc::scoped_ptr<ProcessTask> task) = 0;
+
+  // Adds a module that will start to receive callbacks on the worker thread.
+  // Can be called from any thread.
+  virtual void RegisterModule(Module* module) = 0;
+
+  // Removes a previously registered module.
+  // Can be called from any thread.
+  virtual void DeRegisterModule(Module* module) = 0;
+};
+
+}  // namespace webrtc
+
+#endif // WEBRTC_MODULES_UTILITY_INCLUDE_PROCESS_THREAD_H_