Reland "Move webrtc/{base => rtc_base}" (https://codereview.webrtc.org/2877023002)

Reland the base->rtc_base without adding stub headers (will be
done in follow-up CL). This preserves git blame history of all files.

BUG=webrtc:7634
NOTRY=True
TBR=kwiberg@webrtc.org

Change-Id: Iea3bb6f3f67b8374c96337b63e8f5aa3e6181012
Reviewed-on: https://chromium-review.googlesource.com/554611
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18821}

webrtc/rtc_base/stringize_macros.h

@@ -0,0 +1,38 @@
+/*
+ *  Copyright (c) 2013 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.
+ */
+
+// Modified from the Chromium original:
+// src/base/strings/stringize_macros.h
+
+// This file defines preprocessor macros for stringizing preprocessor
+// symbols (or their output) and manipulating preprocessor symbols
+// that define strings.
+
+#ifndef WEBRTC_RTC_BASE_STRINGIZE_MACROS_H_
+#define WEBRTC_RTC_BASE_STRINGIZE_MACROS_H_
+
+// This is not very useful as it does not expand defined symbols if
+// called directly. Use its counterpart without the _NO_EXPANSION
+// suffix, below.
+#define STRINGIZE_NO_EXPANSION(x) #x
+
+// Use this to quote the provided parameter, first expanding it if it
+// is a preprocessor symbol.
+//
+// For example, if:
+//   #define A FOO
+//   #define B(x) myobj->FunctionCall(x)
+//
+// Then:
+//   STRINGIZE(A) produces "FOO"
+//   STRINGIZE(B(y)) produces "myobj->FunctionCall(y)"
+#define STRINGIZE(x) STRINGIZE_NO_EXPANSION(x)
+
+#endif  // WEBRTC_RTC_BASE_STRINGIZE_MACROS_H_