Move safe_strerror to posix directory and the base namespace

base/posix/safe_strerror.cc

Index: base/posix/safe_strerror.cc
diff --git a/base/safe_strerror_posix.cc b/base/posix/safe_strerror.cc
similarity index 98%
rename from base/safe_strerror_posix.cc
rename to base/posix/safe_strerror.cc
index 9da7aeef1190bd22aca5f203afd90bc5d9639cd3..e80e8f8bd98e2b8b7a13837b160fbc7963312845 100644
--- a/base/safe_strerror_posix.cc
+++ b/base/posix/safe_strerror.cc
@@ -10,13 +10,16 @@
 #undef _GNU_SOURCE
 #endif
 
-#include "build/build_config.h"
-#include "base/safe_strerror_posix.h"
+#include "base/posix/safe_strerror.h"
 
 #include <errno.h>
 #include <stdio.h>
 #include <string.h>
 
+#include "build/build_config.h"
+
+namespace base {
+
 #define USE_HISTORICAL_STRERRO_R (defined(__GLIBC__) || defined(OS_NACL))
 
 #if USE_HISTORICAL_STRERRO_R && defined(__GNUC__)
@@ -117,3 +120,5 @@ std::string safe_strerror(int err) {
   safe_strerror_r(err, buf, sizeof(buf));
   return std::string(buf);
 }
+
+}  // namespace base