htod - convert C .h files to D import files

[Lionello Lunesu]

>>>> * signed char => sbyte
>>> What's the issue?
>>
>> dmd claims (correctly) it doesn't know about sbyte:
>> gl.d(42): identifier 'sbyte' is not defined
>
> <slaps forehead> Arrgh!

Hey! Don't get me wrong! I've posted before that "byte" should be unsigned! 
So, create an sbyte for the signed byte and let's have a laugh about it.

L.