mdoc lang F# sigs fail for ref types

[lobrien]

mdoc lang F# sigs are failing on reference arguments. In the attached image, you can see a failure for:

 <MemberSignature Language="DocId" Value="M:AudioToolbox.AudioFile.ReadPacketData(System.Boolean,System.Int64,System.Int32@,System.Byte[],System.Int32,System.Int32@)" />

Which ends up with two missing arguments :

bool * int64 * {BLANK} * byte[] * int * {BLANK}-> returnType

I think ref args should be byRef<T> but am not 100% https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/byrefs

[joelmartinez]

We need to check if this issue has already been resolved by this PR: #332