mpr: fix a compiler error on PowerPC

[Francois Gouget]

On Fri, 2 Jan 2009, Austin English wrote:

> CHAR defaults to unsigned char on PowerPC, so explicitly setting hi/lo
> to signed char to avoid this error.

CHAR is a Windows type so I don't think it's right for it to be unsigned 
on PowerPC. Even more so since there is a UCHAR type.

So I think the right thing to do is to fix the CHAR declaration in 
wtypes.h and winnt.h.


-- 
Francois Gouget <fgouget at free.fr>              http://fgouget.free.fr/
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