Updating to use the new fnptr syntax and fixing a couple minor issues

[tannergooding]

The alignment and callexpr issues were found when processing libX11 and libVulkan.

[sotteson1]

I'm wondering about this change:

            _outputBuilder.WriteIndented("[UnmanagedFunctionPointer");

            if (callingConventionName != "Winapi")
            {
                _outputBuilder.Write("(CallingConvention.");
                _outputBuilder.Write(callingConventionName);
                _outputBuilder.Write(')');
            }

            _outputBuilder.WriteLine(']');

That attribute seems to only have one constructor that takes the calling convention, but it's left out if the calling convention isn't Winapi. I'm sure I'm missing something, but I don't see how this should work if the calling convention is Winapi.