typedef of missing types

In ecl/config.h line 220 there is a block labelled /* Missing integer types */

The int8_t has a typedef of char which is incompatible with Windows standard types.

https://msdn.microsoft.com/en-us/library/323b6b3k.aspx

changing line 221 from:

typedef char int8_t; to typedef signed char int8_t;

Fixes the issue for me and allows me to compile both lisp code and C++ projects using ecl.lib

I know that char and signed char should be the same but the MS VS compile disagrees.