Upgrade version and change log after branch.

src/version.cc

 // Copyright 2012 the V8 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.
 
 #include "src/v8.h"
 
 #include "src/version.h"
 
 // These macros define the version number for the current version.
 // NOTE these macros are used by some of the tool scripts and the build
 // system so their names cannot be changed without changing the scripts.
 #define MAJOR_VERSION     3
-#define MINOR_VERSION     30
+#define MINOR_VERSION     31
 #define BUILD_NUMBER      0
 #define PATCH_LEVEL       0
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)
 #define IS_CANDIDATE_VERSION 1
 
 // Define SONAME to have the build system put a specific SONAME into the
 // shared library instead the generic SONAME generated from the V8 version
 // number. This define is mainly used by the build system script.
 #define SONAME            ""
@@ skipping 60 matching lines @@
       SNPrintF(str, "libv8-%d.%d.%d%s.so",
                GetMajor(), GetMinor(), GetBuild(), candidate);
     }
   } else {
     // Use specific SONAME.
     SNPrintF(str, "%s", soname_);
   }
 }
 
 } }  // namespace v8::internal