Added compatibility with repr(C) enum types, defaulting to uint type

Having a `repr(C)` enum is syntactically perfectly legal and used,
	even though the specs are not clear on what underlying type is used
	for such an enum. Checking both documentation online and testing
	with several OS (macOS, Windows, Linux) and architectures
	(x86, x86-64 and aarch64) `u32` (i.e. `uint`) seems to be the
	correct choice on all platforms where C# interop is reasonable to
	happen.
	Still, without this a `repr(C)` enum would produce code that
	wouldn't compile at all.

csbindgen/src/emitter.rs

@@ -376,6 +376,7 @@ namespace {namespace}
 
 fn convert_token_enum_repr(repr: &str) -> &str {
     match repr {
+        "(C)" => "uint",
         "(u8)" => "byte",
         "(u16)" => "ushort",
         "(u32)" => "uint",