Windows: Fix build issues on Windows

Generate vulkan.def from header, fix use of alloca
diff --git a/loader/vk-loader-generate.py b/loader/vk-loader-generate.py
index f0fcbdb..d1a5082 100755
--- a/loader/vk-loader-generate.py
+++ b/loader/vk-loader-generate.py
@@ -353,6 +353,8 @@
         for proto in self.protos:
             if self.exports and proto.name not in self.exports:
                 continue
+            if proto.name.endswith("WSI"):
+                continue
             body.append("   vk" + proto.name)
 
         return "\n".join(body)