Add support for VCCLCompilerTool EnableEnhancedInstructionSet setting.

test/win/compiler-flags/enable-enhanced-instruction-set.gyp

+# Copyright (c) 2014 Google Inc. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'targets': [
+    {
+      'target_name': 'sse_extensions',
+      'type': 'executable',
+      'msvs_settings': {
+        'VCCLCompilerTool': {
+          'EnableEnhancedInstructionSet': '1',  # StreamingSIMDExtensions
+        }
+      },
+      'sources': ['enable-enhanced-instruction-set.cc'],
+    },
+    {
+      'target_name': 'sse2_extensions',
+      'type': 'executable',
+      'msvs_settings': {
+        'VCCLCompilerTool': {
+          'EnableEnhancedInstructionSet': '2',  # StreamingSIMDExtensions2
+        }
+      },
+      'sources': ['enable-enhanced-instruction-set.cc'],
+    },
+  ],
+  'conditions': [
+    ['MSVS_VERSION[0:4]>"2010"', {
+      'targets': [
+        {
+          'target_name': 'avx_extensions',
+          'type': 'executable',
+          'msvs_settings': {
+            'VCCLCompilerTool': {
+              'EnableEnhancedInstructionSet': '3',  # AdvancedVectorExtensions
+            }
+          },
+          'sources': ['enable-enhanced-instruction-set.cc'],
+        },
+        {
+          'target_name': 'no_extensions',
+          'type': 'executable',
+          'msvs_settings': {
+            'VCCLCompilerTool': {
+              'EnableEnhancedInstructionSet': '4',  # NoExtensions
+            }
+          },
+          'sources': ['enable-enhanced-instruction-set.cc'],
+        },

[scottmg, 2014/03/11 16:32:58]

Could you add an "unset" test too? It changed from 2010 (IA32) to 2012 (SSE2) by
default, which bit me.

[grt (UTC plus 2), 2014/03/11 17:08:45]

I thought about that. I would need to add a conditional in
gyptest-cl-enable-enhanced-instruction-set.py based on the version of vs being
used. Is there a convenient way to do that?

+      ],
+    }],
+  ],
+}