[tlbuild] -funsigned-char is not portable

[Peter Breitenlohner]

On Wed, 3 Jun 2009, Karl Berry wrote:

> However, Yannis just said that he expects to have one of his students
> work on it this year.  Hope it happens.

Hi Karl, Yannis,

I have just enabled compiler warnings for bibtex8 (svn r13818). There were
plenty of "array subscript has type `char'" warnings plus a few others. 
Replacing Integer8_T by UChar_T (i.e., char by unsigned char) has taken care
of these warnings.  A step in the right direction but I am almost sure more
needs to be done, i.e., carefully deciding where to use Integer8_T or
Unsigned8_T (yet to be defined).

BTW: Once all that is done, one actually should define Integer8_T as signed
char (or maybe not use it at all).

Regards
Peter