Added support of the PlatformToolset property to Gyp (MSBuild only).

pylib/gyp/MSVSNew.py

Index: pylib/gyp/MSVSNew.py
diff --git a/pylib/gyp/MSVSNew.py b/pylib/gyp/MSVSNew.py
index 6906c7bc77460980fae51db987f1b54dbc55f168..edd0085776d2fd8ed7d47eb497aed8bef2cd8621 100644
--- a/pylib/gyp/MSVSNew.py
+++ b/pylib/gyp/MSVSNew.py
@@ -139,10 +139,11 @@ class MSVSProject(object):
     else:
       self.config_platform_overrides = {}
     self.fixpath_prefix = fixpath_prefix
+    self.msbuild_toolset = None
 
   def set_dependencies(self, dependencies):
     self.dependencies = list(dependencies or [])
-  
+
   def get_guid(self):
     if self.guid is None:
       # Set GUID from path
@@ -160,6 +161,9 @@ class MSVSProject(object):
       self.guid = MakeGuid(self.name)
     return self.guid
 
+  def set_msbuild_toolset(self, msbuild_toolset):
+    self.msbuild_toolset = msbuild_toolset
+
 #------------------------------------------------------------------------------