Pull define for version out into v8-version-string.h and separate build target

src/v8.gyp

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 379 matching lines @@
         'action': ['<(mkpeephole_exec)', '<(INTERMEDIATE_DIR)/bytecode-peephole-table.cc' ],
         'process_outputs_as_sources': 1,
       }],
       'sources': [  ### gcmole(all) ###
         '../include/v8-debug.h',
         '../include/v8-experimental.h',
         '../include/v8-platform.h',
         '../include/v8-profiler.h',
         '../include/v8-testing.h',
         '../include/v8-util.h',
+        '../include/v8-version-string.h',
         '../include/v8-version.h',
         '../include/v8.h',
         '../include/v8config.h',
         'accessors.cc',
         'accessors.h',
         'address-map.cc',
         'address-map.h',
         'allocation.cc',
         'allocation.h',
         'allocation-site-scopes.cc',
@@ skipping 2086 matching lines @@
       'conditions': [
         ['want_separate_host_toolset_mkpeephole==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }