deps: make v8.h compatible with VS2015

There is a bug in the most recent version of VS2015 that affects v8.h
and therefore prevents compilation of addons.

Refs: https://stackoverflow.com/q/38378693

Backport-PR-URL: #33376
PR-URL: #32831
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

common.gypi

@@ -36,7 +36,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.5',
+    'v8_embedder_string': '-node.6',
 
     ##### V8 defaults for Node.js #####
 

deps/v8/include/v8.h

@@ -1752,9 +1752,11 @@ class V8_EXPORT ScriptCompiler {
    public:
     enum Encoding { ONE_BYTE, TWO_BYTE, UTF8 };
 
+#if defined(_MSC_VER) && _MSC_VER >= 1910 /* Disable on VS2015 */
     V8_DEPRECATE_SOON(
         "This class takes ownership of source_stream, so use the constructor "
         "taking a unique_ptr to make these semantics clearer")
+#endif
     StreamedSource(ExternalSourceStream* source_stream, Encoding encoding);
     StreamedSource(std::unique_ptr<ExternalSourceStream> source_stream,
                    Encoding encoding);