Support const methods.

Also several enhancements to C decl parser.
diff --git a/specs/stdapi.py b/specs/stdapi.py
index d9fd545..6aa4089 100644
--- a/specs/stdapi.py
+++ b/specs/stdapi.py
@@ -361,10 +361,17 @@
 
 class Method(Function):
 
-    def __init__(self, type, name, args):
+    def __init__(self, type, name, args, const=False):
         Function.__init__(self, type, name, args, call = '__stdcall')
         for index in range(len(self.args)):
             self.args[index].index = index + 1
+        self.const = const
+
+    def prototype(self, name=None):
+        s = Function.prototype(self, name)
+        if self.const:
+            s += ' const'
+        return s
 
 
 class String(Type):