winevulkan: Forward declare required structs for function pointer.

dlls/winevulkan/make_vulkan

@@ -805,11 +805,12 @@ class VkFunction(object):
 
 
 class VkFunctionPointer(object):
-    def __init__(self, _type, name, members):
+    def __init__(self, _type, name, members, forward_decls):
         self.name = name
         self.members = members
         self.type = _type
         self.required = False
+        self.forward_decls = forward_decls
 
     @staticmethod
     def from_xml(funcpointer):
@@ -846,10 +847,19 @@ class VkFunctionPointer(object):
 
         _type = funcpointer.text
         name = funcpointer.find("name").text
-        return VkFunctionPointer(_type, name, members)
+        if "requires" in funcpointer.attrib:
+            forward_decls = funcpointer.attrib.get("requires").split(",")
+        else:
+            forward_decls = []
+        return VkFunctionPointer(_type, name, members, forward_decls)
 
     def definition(self):
-        text = "{0} {1})(\n".format(self.type, self.name)
+        text = ""
+        # forward declare required structs
+        for decl in self.forward_decls:
+            text += "typedef struct {0} {0};\n".format(decl)
+
+        text += "{0} {1})(\n".format(self.type, self.name)
 
         first = True
         if len(self.members) > 0: